If the heating does not work rear window auto in winter period, visibility is significantly reduced, undermining the safety of the driver and passengers. That is why, if a malfunction is detected, you should immediately start repairing.
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How does the heated rear window work?
All schemes for heating the rear window of a car are similar and practically do not differ significantly from each other. AvtoVAZ models, as well as imported cars, are equipped with the same type of design and principle of operation. On the surface of the rear window, thin tracks are applied - conductive threads. The electricity passing through them causes them to heat up. On the outside of the glass, snow and ice quickly melt, and the inside of the surface gets rid of fogging.
Heating circuit
Before troubleshooting the device and trying to fix them, you should familiarize yourself with the heating circuit and understand the components necessary for its stable operation.
Auto rear window heating circuit
Decoding the scheme:
- 1 - conductive threads;
- 2 - indication on the instrument panel;
- 3 - on / off button;
- 4 - ignition lock;
- 5 - relay;
- 6 - mounting block.
In the video, you will learn how to repair the heated rear window yourself. Video provided by EXPERIMENT _ TV.
Possible device malfunctions
If the heated rear window does not work, then one of the components listed above is out of order or its electrical circuit has been broken. You can check all the nodes of the heating device yourself if you have at least the slightest idea of \ u200b \ u200bthe repair of machines. Below we will consider in detail the reasons for the malfunction of each node.
System fuse
Initially, if heating problems arise, make sure the safety element is intact. Its burnout will affect the performance of the device. Each car manufacturer places this fuse in different places in their models. To quickly find its location, it is recommended to use the vehicle operating instructions or service book.
It is necessary to remove the found element and check for suitability. A blown fuse should be replaced with a new one, otherwise further attempts to troubleshoot the heating of the glass will be meaningless.
Relay
One of the reasons for the failure of the glass heating operation may be a relay malfunction, this element is located in mounting block... The relay turns off the heating when the motor stops running. This device cannot be restored, therefore it is replaced with a new one.
Wiring faults
If the fuse and relay are in good condition, it is required to diagnose the electrical wires. They probably broke, burned out or broke off at the attachment point. In this case, the heating strips will not be energized.
They test the condition of the power supply wires as follows:
- You need to turn on the heating button.
- Using a multimeter, check the voltage at the first and second terminals for connecting wires to the heating "tires". They are located at the bottom or on both sides of the glass. Lack of voltage causes the heater to malfunction.
The first thing that needs to be done in this case is to clean the terminal contacts and all connection sections, they can oxidize and not pass current. If the tester still reads "0", then there is an open circuit somewhere in the wiring. A visual inspection of the entire path of the electrical circuits is carried out. Having found suspicious or damaged areas, you need to connect them, since there may have been a break in these places.
Threads
Heating strips are also susceptible to damage. Before looking for a problem area, you should familiarize yourself directly with the workflow in threads.
The voltage is supplied to the entire heating unit and is evenly distributed over each parallel-connected tape. As a result, these tapes act as conductors of electric current. Due to resistance, they are heated to a low temperature, which is quite enough to remove ice and snow from the glass surface. If the integrity of one of the threads is violated, the electric current will stop circulating through it, and heating of this area of the glass will not be performed.
Violation of the integrity of the thread
Governing bodies
When you press the button, the indicator should light up, notifying about the start of work. If the switch is activated, the indicator is on, and heating still does not occur, then the button contacts have become unusable. As a result, no power is supplied to the heater. A worn out toggle switch cannot be repaired - a new one must be installed.
DIY heating repair
The most common cause of non-working heating is damage to thin conductive filaments. Modern technologies make it possible to restore sections of breakage of these threads with their own hands without the involvement of specialists.
Finding the location of the thread break
First you need to find the damaged areas of the threads. The process will not take long, since the cliffs are perfectly visible to the naked eye. It is extremely rare to find minor damage that is difficult to see, in which case you need to use a voltmeter.
The thread has a resistance of 10 ohms, each section has its own voltage. On the first - the voltage is twelve volts, on the third - already six, and on the fifth - zero. To find a break, measure the voltage at the center of each element. If there is damage, the multimeter will give 12 or 0 volts, from here it is clear that there is a break on the left or right side of the filament.
Troubleshooting a heater with copper solution
For work you will need:
- sulphuric acid;
- copper rod, up to 10 mm in diameter;
- copper sulfate;
- a strip of fabric 50x30 cm;
- Scotch;
- scissors;
- glass cleaner.
You need to repair damage to the conductive thread as follows:
- At the first stage, it is important to prepare the damaged surface for restoration work. To do this, we use a rag soaked in alcohol and wipe the glass with it. When the dirt is completely removed, degrease the surface.
- We glue adhesive tape on both sides of the conductive thread at the break point. We attach the adhesive tape so that the width between the strips corresponds to the heating thread.
- A copper rod is wrapped with cloth at one end. We fix the so-called brush with threads.
- A copper solution is being prepared. Half a glass of water is thoroughly mixed with two teaspoons of copper sulfate. A little highly concentrated sulfuric acid or electrolyte from car batteries is added to the resulting liquid.
- The terminals from the heating device are connected to ground. The wire from the "positive" terminal of the battery is connected to a previously made brush from a metal rod.
- The resulting electrode, soaked in the solution, is carefully rubbed over the sections of the broken threads. The ends of serious breaks are pre-processed with an electric soldering iron. It also installs a connecting jumper made of the thinnest wire. As a result, slightly damaged areas are covered with copper.
Troubleshooting a heater with conductive adhesive
Conductive glue is a specialized paste that contains fine powder of palladium, as well as nickel, gold or silver. Thanks to the listed elements, this substance perfectly conducts current and has good connecting properties. The process of restoring the heating filaments of the stern glass with conductive glue is faster and more efficient. 
To start restoring the threads, we perform the same procedures for cleaning the glass surface and pasting the damaged area with tape. For the preparation of conductive glue in the repair kits, two substances are provided, which must be thoroughly mixed in a separate container. How to prepare the composition and further use it for its intended purpose is written in the instructions on the package.
The glue is applied with a brush or cotton swab, the layer size should not exceed 2 mm. The average solidification time of the conductive compound is 30 minutes. After 24 hours, we remove the excess substance, this is done with a knife or any sharp object.
When removing excess conductive adhesive, proceed with extreme caution, otherwise the surface of the heating device will be damaged again.
Video "Repair of rear window heating filaments"
Detailed explanation of heating filament repair. The video was taken from the channel "BortZhurnal Renault Megan".
While creating passenger car the designers pay great attention to the glazing of the machine. In construction vehicle glasses play an important role. They protect the driver and passengers from wind, dust and dirt. Serves as a soundproof barrier that allows people in the cabin to talk without stress.
Visibility from the passenger compartment and the driver's ability to control correctly depends on their shape. traffic situation... For this, various modifications are made to the windows, including heated rear window.
The system to help clear the rear window from ice, snow or fogging is not very complex structurally. The electrical diagram can be broadly depicted as follows:
- C - generator.
- E230 - OZS system switch.
- J519 - Onboard power supply control unit.
- Z1 - heating element of the OZS system.
Although on different models cars and there may be some differences, however, if we consider it in detail, then, in principle, it includes the following main elements.
- Mounting block.
- Ignition switch.
- ZS heating switch.
- Control lamp signaling the inclusion of the OZS.
- Heating element of the OZS system.
K6 - additional relay.
K7 - relay for switching on the OZS.
A - connection to power systems.
In addition, the system contains fuses, terminals and wires that connect all the elements into a single whole.
When the ignition key is turned, the OZS is turned on by pressing a button, to which power is supplied through an additional K6 relay. At the same time, the relay for heating the rear window K7 is activated, the heating element is connected and at the same time the control lamp comes on.
The design of the heating element on the rear window can also be different. In the standard version, it is a mesh of thin metallic nickel threads that are connected by two conductive busbars located on opposite sides. On the one hand, a current of 12V is supplied to the bus, on the other, the bus is shorted to ground. Such devices are attached to the glass with a special glue.
On some car models, the heating element is applied to the glass using a coating, for example, aluminum. On top of such spraying, a thin film with good light transmission is attached using a conductive glue.
Identification of malfunctions in the OZS system
Having found signs that the rear window heating is not working, you need to carefully check the entire electrical circuit of the vehicle's NEO system.
The first thing to check is that the fuses are working properly. So, for example, on the VAZ-2110 these are rear window heating fuses F4 and F7, which are located in the mounting block. Their malfunction may occur due to a factory defect, short circuit or voltage surge in on-board network... A defective fuse needs to be replaced, for which it must be removed from the mounting block.
Next, you need to check the terminal connections in the OZS system. When operating a vehicle, all equipment is affected by strong vibrations... As a result, the contacts may be damaged, or a terminal may become disconnected or weakened.
A check of the heated rear window relay is also required. Breakdown of the relay is possible when a wire breaks in the working coil of this part or due to burning of the contacts, due to a factory defect or short circuit. To check it, the relay must be removed and checked with a tester. In the event of a malfunction of this part, you need to replace it with a workable part.
It is also necessary to check the contact of the heated rear window. A conductive element is attached to the rear window with glue, which is a contact to which an electric current is supplied through the wiring, which is transmitted through this contact to the heating threads.
In this place, a break in the wiring is possible or due to the fact that the glue was of poor quality, the contact element peels off from the glass.
Quite often, a breakage or damage to the threads in the heating element on the rear window leads to failure of the ES heating. This is detected by visual inspection or instrumental analysis. Visually, only a clear damage to the thread can be detected by establishing a gap between the damaged ends.
It is possible that for some repair work a mechanical damage to the glass surface was inflicted on the car, on which a heating element was attached with glue.
However, the main tool in diagnosing this malfunction is a voltmeter or ohmmeter.
They make it possible to identify with high accuracy a section with faulty threads, even if this break cannot be visually detected.
Repair procedure for a faulty OZS system
Having determined the reason why the rear window heating does not work, you can start repairing this system.
- If the fuses or relays of the NEO system are faulty, then the faulty parts must be removed. Replacing them with new, efficient labor does not constitute. The main thing is that they are installed as indicated by the diagram of the electrical on-board system.
- In the case when the culprit for damage in the OZS system is the terminal connection, the restoration of the heated rear window is also straightforward. It is enough to clean the contacts in the terminals. It may be necessary to replace the terminal box, but this also does not take much time.
- If the glue that attached the contact on the rear window turned out to be of poor quality and delamination occurred, then in this case you need to buy a new high-quality conductive glue. Remove the layer of old glue from the detached contact using a napkin with an alcohol solution. Then apply a coat of new bonding agent and glue the contact in place.
- If a wire break is detected on one of the buses, it is necessary to solder this wire to the old place using the connection diagram. The procedure is as follows:
- remove the remnants of the old solder from the wire by stripping the end, in addition to this, the junction on the bus must also be cleaned;
- using a brush, apply rosin paste as a flux to the cleaned surfaces of the bus and wires;
- apply a solder containing three percent silver to the cleaned and roasted wire core;
- solder the wire to the bus, while avoiding overheating of the surfaces.
- Most of all accuracy when repairing the rear window heating with your own hands is required if a break is found in the conductive threads of the OZS heating element. To facilitate this work, special repair kits for this system are available commercially. To fix the damage, the actions are performed in the following order:
- in the area of the gap, clean an area six millimeters long in each direction from the place of damage;
- wipe the cleaned area with a napkin or a cloth soaked in alcohol or alcohol solution;
- on both sides of the damaged thread, stick thin strips of repair adhesive tape or ordinary construction tape, if there is no repair kit. Do not allow sticking of adhesive tape on nearby threads, in order to avoid damage to them;
- if there is a repair kit, then mix the hardener with a silver-colored composition, which, after application, will act as a conductive thread. After mixing, apply this compound with a stick or brush to the damaged area, closing the chain.
- if there is no repair kit, then the role of a special mixture will be played by glue, which conducts electric current well, it can be applied with a brush, observing accuracy;
- after repairing the damage, it is necessary to give time for the glue or a special mixture to harden; a hairdryer can be used to speed up this process;
- after the strip that conducts the current has dried, it is necessary to carefully remove the self-adhesive tape, for this it is best to cut it with a knife at the point of abutment to the thread being repaired so as not to damage it when removing the tape;
- after the work performed, it is necessary to check the operability of the OZS, for which start the car engine and press the OZS ON button.
See also video
Good afternoon. Today we will talk about how to repair a heated rear window. Traditionally for our site, the article contains a lot of photos and videos and is a step-by-step troubleshooting algorithm.
How does glass heating work?
I think everyone remembers the physics from the high school course. When an electric current flows through a conductor, it heats up. It is on this principle that the rear window heating works.
If you look closely at the glass, you will see contacts and current supply wires from the sides.
When a voltage is applied to these terminals, an electric current flows through the heating filaments and heats the glass, thereby making it.
Accordingly, glass heating does not work in only two cases:
- heating threads are faulty
- no voltage at the terminals
How to repair the heating if one or more heating threads are faulty?
This malfunction looks like this:
For repairs we need:
- sandpaper with a number from 1500 to 2500, 1 sheet of any grain. It is needed to remove oxides and varnish from places of damage to the threads.
- alcohol, preferably isopropyl (we will use it to wipe the glass from dust and degrease the damage)
- napkins, microfiber, cotton swabs or rags (for cleaning).
- conductive adhesive, in stores it is not always available, so if you are ready to wait, I recommend ordering it directly from China (we will use it to restore damaged threads).
Repair procedure:
We carefully examine the faulty heating threads and look for damage, they usually look like this:
We carefully clean the places of damage with sandpaper, trying not to touch the glass, we only clean the heating threads themselves and then next to the damage. If you rub the glass itself with sandpaper, it will become dull, but it will not come out, since the heating threads are not applied to it.
Wipe cleaned surfaces with alcohol using a cotton swab. In this case, we will remove the dust from the sandpaper and degrease the surface.
Gently apply conductive glue to the damaged areas. In order to apply the glue directly and not as a stain, it is better to use duct tape or masking tape. As shown in the video at the end of the article.
Apply conductive glue with a brush.
We wait until the glue dries, check it, make sure that everything works and enjoy the money saved….
What if the heating does not work at all?
If the heating does not work at all, there are two options. Either all the heating threads are faulty (this is unlikely, even on machines that are 30-40 years old, one or two threads heat) ... Or the wiring is faulty.
A person without special education can only check 3 things:
The location of these items can be found in the operating instructions for your vehicle.
If, after checking, by the replacement method, your heating has not worked, it is better to contact an electrician at the station of those. service.
How to repair the heating if the glass is tinted?
I don’t want to upset you, but most likely the answer is no way! Since, in order to apply electrically conductive glue, you will have to locally (locally) remove the tint anyway. I'm not sure if you can cut a piece of tinting with just a damaged thread. In any case, you will get an ugly hole in the toning….
Therefore, if you need to repair one or more heating filaments on tinted glass, unfortunately, the tint will have to be removed.
Conclusion.
As you can see, the repair of glass heating is not difficult, of course, with due care and desire.
Obviously, the easiest option is not to repair the threads, but to replace the glass, but think about how, because if the buyer sees glass from different years of production, then at least they will tell you that the car was a bit.
That's all for me today. I hope that you have no questions about how to repair the heated rear window. If you have any questions, or if you want to supplement the article, write comments.
There are such malfunctions in the car in which you can drive as before, but they constantly bother you, cause unpleasant feelings. Such malfunctions include the failure of the glass heating circuit at the rear of the car.
Usually, this electrical circuit is always amenable to repair. And there are troubles with these threads for the following reasons:
- crack in the window;
- failure of contacts;
- open circuit;
- natural wear and tear of a part of the track on the window;
- mechanical scratching of the track.
The most common thread break occurs on the window. Sometimes it can be determined visually, but more often with the help of an instrument. Next, we will figure out how to diagnose, and how to repair the heated rear window.
How to restore heat with glue
Let's analyze stepwise process do-it-yourself repair of heating the rear window when the thread breaks. Useful for us:
- electrical tester;
- conductive adhesive used for glass repair;
- tin foil;
- Scotch;
- thinner, clean cloth.
Read also about and.
You can buy special glue for repairing the heated rear window at a regular auto shop. We start repairing damaged heating threads by turning on this system button in the salon.
- First of all, we determine the place of the gap. To do this, turn on the tester in the voltmeter mode and, applying the foil to the thread on the window, check the thread through the foil with a probe, moving from the positive contact. In this case, we apply another probe to the negative contact of the heater.
- At the break point, the voltage will jump from zero to several volts.
- Next, wipe the rupture site with a solvent.
- We glue the tape on the top and bottom of the thread, leaving a distance for the thickness of the thread.
- We apply conductive glue for repairing heating threads with a syringe or brush. It all depends on what is offered in the set with glue. In addition to the empty space in the gap, we coat another centimeter of each end of the whole thread.
- We remove the scotch tape. We wait about 24 hours until the glue is completely dry.
- We remove the excess, wipe the place of repair.
This is how the damaged threads of heating the rear window are repaired with their own hands. It is clear that you will have to buy a set with glue beforehand.
What to do with contacts and other methods
Now let's talk about how to repair broken rear window heating contacts. To do this, you must first understand the principle of building this electrical circuit.
It turns on only when the ignition is on, an additional relay is responsible for this. It supplies power to the system button. When the button is on, the lamp lights up in parallel and the switching relay, powered by the fuse, is activated. Further, the voltage is supplied to the heating threads.
Repair of glass heating contacts consists in restoring their performance. To repair any faulty rear window heating terminal, we need:
- multimeter;
- screwdriver;
- soldering iron, solder, rosin.
All the manipulations described below are available on the Internet as a video with the title: "DIY glass heating repair." We will write further in words. So the actions are like this.
- We check all the elements of the circuit to find the location of the malfunction. First, we look at the fuse.
- Next, we check the serviceability of the button by measuring the contacts with a multimeter when it is turned on.
- We check the relay, when it is triggered, the corresponding contacts should give out a voltage of 12 V.
- We measure the voltage of the connector at the rear window.
- We check all the wires going from the button and relay to the heating track system, see what the state of the insulation is, if there is any short circuit to the car body.
- We restore the faulty place by replacing the terminal, additional insulation or soldering the contact.
This is how the contacts for heating the rear window of the car are repaired. If the chain break is on the threads, then we find a specific place according to the algorithm already described above with the help of a tester. Further, in the absence of purchased glue, you can fix the thread break like this.
Let's prepare:
- brass or copper bar;
- file;
- red paint;
- Scotch.
- Use a file to prepare brass or copper shavings.
- Mix the paint with the shavings in a 1/1 ratio.
- We turn on the heating.
- We glue the adhesive tape on top and bottom of the faulty area, leaving a distance commensurate with the thickness of the thread. We clean this area.
- We apply a composition of paint and shavings.
- We wait for drying for a few minutes. We remove the scotch tape.
This is such an interesting technology. There is another option for restoring the lost section of the heating track in the absence of special glue. Let's consider it on the example of a specific car.
To repair the heated glass at the rear of Renault Logan, we need to use the following accessories:
- copper sulfate (purchased at a fertilizer store);
- battery electrolyte (sold in any auto shop);
- a piece of copper bar with a diameter of about 6 mm;
- a piece of regular cloth.
This method is called electrolytic. You need to make the following manipulations.
- Wrap the end of the bar with a piece of fabric so that the tip hangs down slightly, and, moreover, fix it so that it does not fall off.
- You can prepare a solution for work in the following proportion: half a glass of water plus two teaspoons of copper sulfate, literally a hundredth of the electrolyte. Stir everything.
- We connect a bar with a rag as an electrode to the positive terminal car battery... In this case, the contact of the thread on the glass with a minus of the chain must be serviceable.
- The resulting positive electrode is dipped into the solution and driven along the lost area of the heating track. The copper from the solution should cover the entire area.
This method works well for all small scratches. In addition, it is not as difficult to perform as it might seem at first glance.
Heat recovery price
However, if you still do not want to do anything yourself, it is enough to contact a car service, where the entire electrical circuit will "ring" completely, quickly find the place of the defect and professionally fix it.
And what is the price for glass heating repair is spelled out in the following table. Here it is - with average data for large Russian cities.
| Town | Price |
| Moscow | RUB 1100 |
| St. Petersburg | 1050 RUB |
| Ekaterinburg | RUB 1000 |
| Samara | RUB 900 |
Here are the values obtained during work of average complexity on a popular budget foreign car. For VAZ it will turn out a little cheaper - by twenty percent. It's just that car services always charge a little less for domestic cars, it so happened, although somewhere the mechanisms are simpler arranged on foreign cars.
Good visibility is essential for safe operation car. In the autumn-winter period, the glass fogs up due to changes in air temperature, and visibility through them deteriorates. The issue of glass transparency in dark time days, when visibility is already bad.
An effective way to combat fogging of car windows is to heat them. Windshield, as a rule, it is heated by directed streams of warm air. The rear window and rearview mirrors are usually heated using electricity. Conductive paths made of high-resistance metal in the form of thin ribbons are applied to the glass surface from the side of the car interior. When an electric current passes through them, thermal energy is released. The glass heats up and the water evaporates. After a few minutes, the glass becomes transparent.
Heater wiring diagram
To successfully diagnose and repair the rear window heating system of a car at a professional level, it is necessary to know the wiring diagram of the heater and to understand the principle of its operation.
The photo shows a typical diagram for connecting a car rear window heater to the on-board wiring. Let's consider how it works.
The supply voltage from the positive terminal of the battery through the ignition switch, and the fuses are supplied to the heater switch and to the 30 (or 87) power contact of the relay. The negative terminal of the battery is connected to the car body, one of the terminals of the glass heater is also connected to the body. When you press the heater power button, the voltage is applied to the relay coil, the relay is triggered, the power contacts close and connect the relay terminals 30 and 87 to each other. The current enters the heater, flows through a group of parallel-connected threads and returns through the car body to the negative terminal of the battery.
Rear window defogger malfunctions
The functionality of the rear window defroster is ignored until the glass fogs up or becomes covered with frost. After turning on the heater, it is suddenly discovered that after a few minutes the glass did not become transparent or that visibility appeared only through a part of the glass. Depending on the external manifestation, even without measuring instruments, one can immediately make an assumption about the cause of the failure.
Please note that the rear window and rear-view mirrors heater can only be turned on when the ignition key is set to the ON position. In some car models, the heater can only be turned on when the engine is running. This is done to prevent a strong discharge of the battery, since the rear window heater, depending on the car model, consumes a current from 10 A to 25 A. For comparison, one headlamp consumes a current of only 5 A.
Heater does not turn on
If the indicator on the button for turning on the rear window heating does not light up after pressing it, then the fuse is most likely blown or the key itself is faulty. If the indicator is on, but not a single thread heats up, then the cause of the malfunction may be a relay or connectors for connecting the heater to the wiring. In this case, according to the documentation for a specific car model, it is necessary to determine the location of these parts and replace the failed one. It is not always possible to quickly find the place of installation of the relay, but there is a way to check its serviceability in an indirect way, which will be discussed below.
The glass is slowly sweating
Sometimes there is a case when, after turning on the heater, the glass sweats for a time significantly exceeding a few minutes. In this case, if it is not very cold outside, the reason may lie in the poor contact of one of the connectors. electrical circuit... As a result, the contact resistance increases, the current is limited, and as a result, the power released on the glass heater filaments decreases. To check such a malfunction, you need a voltmeter direct current(with a multimeter or a pointer tester, included in the DC voltage measurement mode), measure the voltage at the input terminals of the heater and battery. Voltages should not differ by more than one volt.
Horizontal misting stripes remain on the glass
And finally, the most common case of a malfunction in the rear window heating system of a car, breakage of one or more threads of the heater applied directly to the glass. This type of malfunction is immediately visible on the horizontal strip of the remaining fogging on the glass after turning on the heater.
The conductive tracks on the rear window have low mechanical strength and are easily destroyed when exposed to them. Therefore, it is forbidden to remove frost and ice from the glass with a scraper. Only wipe with a soft cloth. It is also necessary to ensure that when transporting bulky items, they do not run into the rear window. As a rule, individual heater filaments stop working as a result of their accidental mechanical destruction. After turning on the heating, stripes of fog or frost remain in the area of the damaged thread.
When renovating an apartment, I was transporting floor skirting boards in my car and did not notice how one of them rested against the rear window. After a while, when it was necessary to warm up the rear window, I saw the result of my inattention. Two strips of the heater, passing through the middle of the glass, did not heat up, which significantly impaired the view of the road. Upon visual inspection, on the non-working strips, one gap of about 1 mm wide was found, as in the photograph. The question arose about the need to repair the rear window heater.
How to find a broken glass heating thread
It is not difficult to determine which thread of the heater in the cliff, since in the zone of its passage the fogging does not disappear during the operation of the heater. Therefore, in order to make it easy to find a faulty thread during repair, it is advisable to count the threads from top to bottom and remember which one is in the cliff, so that then by visual inspection try to find the place of its damage. But the thread break is so small that it is impossible to find it visually. Then a DC voltmeter, ohmmeter or voltage indicator will help in the search. To quickly find the place of a malfunction in a heating element, you need to imagine how it works and works.
The device of the heating element of the glass heating system
The question is logical, why does it happen that only one or several threads in the heater do not work, and the rest work? To get an answer to this question, you need to familiarize yourself with the design of the heating element.
The heating element of the rear window of the car is arranged as follows. On the lateral sides of the rear window, two conductive bars 1 and 2 are applied. To these bars, threads of high-resistance material are connected. Each of the strands has a resistance of about 10 ohms. The number of threads depends on the height of the glass. Thus, each thread is a separate heating element, the operation of which does not depend on others. The scheme of parallel connection of heating elements is applied. Such a circuit design ensures high operational reliability of the heater, since the breakage of one or more threads does not lead to a complete cessation of its operation.
Finding a broken filament heater using a voltmeter
For work, you will need any DC voltmeter with a measurement limit of 15 V. As a voltmeter, any dial tester or digital multimeter is suitable. Before starting work, you need to turn on the heater.
Since one of the tires of the heating element is connected to the car body, the negative terminal of the voltmeter can be connected to the car body; any screw or bolt screwed directly into the body will do. It is most convenient to attach the alligator clip to the boot lid lock bracket.
Since visually with a transparent glass it is difficult to find out whether the heater heats up, then by touching the positive probe of the voltmeter to bus 1, and then to bus 2, you will immediately understand this. The voltage on bus 1 should be +12 V, and on bus 2 - 0 V. It is possible that the left bus in your car will be connected to ground, and on right tire the supply voltage will be applied. If there is no access to the tires, then measurements can be taken by touching any of the threads with a probe at the points of connection with the tires, that is, in the places where they exit from the rubber seal. In the photo, these are points 1 and 5.
Using a voltmeter, it is easy to determine which part of the heating system is faulty. If the heater is on, the on indicator on the button is on and there is 12 V on bus 1, but there is no heating, then the wiring to bus 1 is working properly. If there is no voltage on bus 1, then there is a bad contact in the supply voltage supply terminal on bus 1, or the relay is faulty. If 12 V is present not only on bus 1, but also on bus 2, then you need to look for a bad contact in the terminal for connecting the wire to bus 2 or in the circuit for connecting the wire to the vehicle ground.
Finding the location of the thread break
After checking the power supply system to the heater, you can begin to determine the location of the breakage of the heating thread. The thread is a tape resistance of about 10 ohms, and therefore the magnitude of the voltage at its different points has a different magnitude. Therefore, at point 1, the voltage will be 12 V, at point 3 - 6 V, and at point 5 - 0 V. Therefore, even without knowing which of the threads is in the cliff, it can be easily found by measuring the voltage in the middle of the length of all threads. On the broken threads, the voltage will be 12 or 0 V. If the voltage is 12 V, then the break point is on the left, and if 0 V, then on the right.
Now it is enough to slowly hold the probe towards the break, in the place of a sharp change in voltage and there will be a gap. For example, in the photo this is a section of a thread between 6 and 7 points.
Finding the broken thread with an ohmmeter
Using a multimeter or pointer tester in the "title =" mode (! LANG: How to measure resistance">измерения сопротивления тоже успешно можно найти место обрыва нити. Включать обогреватель при поиске омметром не нужно, но проверить исправность системы подачи питающего напряжения на нагреватель, кроме проверки цепи подключения к массе, не получится.!}
If the broken thread is not known, then you need to connect one end of the ohmmeter probe to the ground terminal, and touch the middle of the heater threads with the second in turn. The thread on which the ohmmeter will show resistance is twice as large and will be in a cliff. For reference, the resistance on whole strands relative to bus 1 or 2 should be 2-3 ohms. In the event of a break in the filament, the ohmmeter will show 4-6 ohms.
When the damaged thread is found, it is necessary to move the end of the probe from the center to any side. If the resistance increases when the probe moves towards tire 1, then the break is in the gap between tire 1 and the touch point of the probe. For example, in the place indicated by points 1 and 2. As soon as the probe passes the break, the resistance will sharply decrease several times. If the resistance decreases, it means that the thread breakage is between the probe and the bus 2. For example, in the place indicated by points 3 and 4. Then you need to move the probe towards the bus 2, and when the resistance drops sharply, at this point there will be a break ...
Finding the location of the thread break
with Automotive Probe Tester
If a voltmeter or ohmmeter is not available, then you can find the place where the filament of the heating element breaks with the help of a home-made automotive tester probe, consisting of just any one LED and a current-limiting resistor. I have made such a tester for myself a long time ago, although I have any measuring devices at my disposal. A homemade automotive test tester is always in the glove compartment of my car and I had to use it more than once.
Finding a broken thread with a tester probe is not much different from searching with a voltmeter. The indicator in this case will be not an arrow or numbers, but the glow of the LED.
Before starting the search for a damaged filament with a probe, it is necessary to apply a supply voltage to the heater. First, the presence of voltage on bus 1 is checked, the LED should be on, if the LED is off, then the fault lies in the supply voltage supply circuit. Next, the voltage on bus 2 is checked, the LED should not light up, if it is on, it means that there is a contact failure at the point where the wire is connected to the bus or the car body.
To find the place where the heater filament breaks, you need to slowly, lightly touching the filament, lead along it with the end of the probe. At the point at which the LED turns off or lights up and there is a thread break. For example, at point 6, the tester's LED will glow, and at point 7, it will not. In my case, the thread breaks were large and the tester was only useful for checking the quality of the repair.
Heating element filament repair methods
There are several ways to restore the working capacity of the heating thread at home.
Using conductive pastes and adhesives
The simplest and most effective is with the help of special repair kits, for example, DONE DEAL DD6590, designed to repair the threads and contacts of the rear window defogger by both amateurs and professionals. The method is good because it does not require tools and materials. It is enough to apply a little conductive paste according to the attached instructions to the place where the thread breaks from the syringe, wait until the paste hardens and the repair is completed. But such a set costs more than $ 15.
The second method is similar to the previous one. But instead of a proprietary set, purchased conductive adhesives are used, for example, "Elekont", a Moscow manufacturer. The glue is applied to the place where the thread breaks, overlapping the whole part of the thread by a centimeter on each side. To get a neat look, a stencil made of electrical tape or scotch tape is used. For reliability, the glue is applied two times. Between the layers of conductive glue, it is advisable to lay a piece of tinned copper wire with a diameter of 0.3-0.5 mm.
It is believed that a conductive paste or glue for repairing glass heater threads can be made independently by mixing paint or glue with brass sawdust in a one-to-one ratio. The resulting composition is applied through a stencil in a thin layer to the thread breakage in several layers. But the reliability of this technology has not been confirmed by practice.
Electroplating copper
Another method is copper electroplating. The heater filament repair method seems attractive. But from my personal experience, I can say that the reliability of such coatings at home is low. So I hesitated to use this technology.
By soft soldering
The mechanical method of restoring the integrity of the rear window heater filaments by soft soldering has become widespread. The reliability of this method has been tested by me when repairing rear window heating filaments in my own car. Given below step-by-step instruction, written on the basis of my experience, will allow you to easily repair the heater thread yourself in just a few minutes with virtually no financial costs.
On the advice of theorists from the Internet, I made a big mistake, tried to strip the thread with sandpaper. As a result, instead of breaking a thread with a width of 1 mm, a break of more than 1 cm turned out. The thread tape is very thin, with only a couple of tens of microns and is erased, even with the finest-grained sandpaper, instantly. The heater threads are not covered with anything anyway, and it is enough to degrease the soldering area with a rag dipped in alcohol or acetone.
If the width of the thread break is less than 1 mm, then you can do without soldering the additional conductor. In my case, the width of the gap was large, and I had to pre-prepare a piece of copper wire for the jumper. A current of about 1 A flows through one thread of the heater. Based on this, we select a wire with a cross section of 0.17 mm 2, which corresponds to a diameter of 0.45 mm, according to the wire cross-section table. The length of the copper jumper should be equal to the width of the thread break plus 2 cm. Before soldering, the jumper must be tinned with a thick layer of POS-61 tin-lead solder. There is no need to tin the heater thread.
In order for the solder to reliably adhere to the heater thread, before soldering the jumper, grease the thread in the soldering zone with a brush with a thin layer of zinc chloride flux.
Next, the jumper is pressed against the heating thread and heats up for one second with a 12 W soldering iron. The hand is pulled to the side. The jumper should be kept on the string. Trying to pull it to check the quality of the soldering is unacceptable, it will fall off, and also tear off a piece of the heater thread. Unfortunately, it has been tested empirically. As a result of experiments, I ended up having to solder the jumper 5 cm long.
After soldering one end of the jumper, the other is pressed tightly to the thread and also warmed up with a soldering iron. After the end of soldering, in order to remove the acidic flux residues, the glass is thoroughly washed with water.
To top it off, for reliability, although it is not necessary, I covered the soldered jumper on top with a transparent superglue "Moment" based on cyanoacrylates, the heat resistance of which is about 70 ° C. The heater does not heat up above this temperature.
As a result, the time to repair a broken thread with your own hands, taking into account all preparatory work was no more than ten minutes. The repaired threads have been in service for over three years.
