Additional heating of the rear window of the car. Rear window heating restoration. How does heated rear window work?

Good visibility is essential for safe vehicle operation. 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 is especially relevant at night, when visibility is already poor.

An effective way to combat fogging of car windows is to heat them. The windshield is usually 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, 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.

It should be noted that the rear window and rear-view mirrors heater can only be switched 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 of 10 A to 25 A. For comparison, one car headlight consumes a current of only 5 A.

The 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.

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 of the 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, it is necessary to measure the voltage at the input terminals of the heater and battery with a DC voltmeter (multimeter or dial tester, included in the DC voltage measurement mode). 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 of 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 rest against 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 easily find a faulty thread during repairs, it is advisable to count the threads from top to bottom and remember which one is in the cliff, so that you can then try to find the place of its damage by visual inspection. 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 buses 1 and 2 are applied. To these buses, 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 several 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. Bus 1 should have +12 V, and bus 2 should have 0 V. It is possible that the left bus in your car will be connected to ground, and the right bus will be supplied with supply voltage. 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 filament 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 value 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 with the second, in turn, touch the middle of the heater threads. The thread on which the ohmmeter will show the resistance is twice as much 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 thread, 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 is broken using 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 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 probe tester 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.

Methods for repairing heating element filaments

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 defroster by both amateurs and professionals. The method is good in that 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 the electroplating of copper. 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 was tested by me when repairing rear window heating filaments in my own car. The step-by-step instructions given below, written on the basis of my experience, will allow you to easily repair the heater thread yourself in just a few minutes with practically 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 gap 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 from the table of wire cross-sections, which corresponds to a diameter of 0.45 mm. 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 thread break with your own hands, taking into account all the preparatory work, was no more than ten minutes. The repaired threads have been in service for over three years.

Freezing and fogging of the rear window leads to a decrease in visibility, which limits control over the traffic situation. In the article, we will consider all the heating components, as well as their possible malfunctions. We will show you how the rear window heating is repaired.

How the system works

To easily find a malfunction of the rear window heater, consider the system design. All elements are presented in the schematic diagram.

Mounting block.
Heating switch relay.
Egnition lock.
The button on the dashboard. A light is installed inside the button, which lights up when the heating and ignition are on.
The corresponding icon on the dashboard, duplicating information about the included heating.
Conductive threads located on the rear window.

The principle of operation of the entire system lies in the heating effect, which manifests itself when current passes through the heating element. Such in the rear window heating system is a network of conductive threads. When the ignition is turned on in the 3rd position (On) through the fuse (in our case, F7), power is supplied to the system power button. After pressing the button, the current, lighting the control lamp, flows to the corresponding icon on the dashboard and back to the mounting block to the switching relay. After the corresponding contacts of the relay are closed, power is supplied (+) to one of the terminals of the system of conductive threads. The second terminal is connected to the car body corresponding to the negative terminal of the battery. Thus, a current begins to flow through the threads.

Now it is easier for us to understand how to repair the heated rear window. For a successful repair of a heated rear window of a car, it is advisable to be able to read electrical diagrams, since not for all cars you will find such clearly depicted elements as in the diagram provided by us.

Malfunctions

How to find the reason

All manipulations to find the cause of the breakdown should be done after checking the fuse. Also, the very nature of the breakdown can often suggest a way to troubleshoot.

For example, together with the heated rear window, the light in the button stopped working. It is likely that this is just a coincidence, as the light bulb may have simply burned out. But the contiguity speaks of the likelihood of no power going to the button. In this case, according to the above diagram, you need to check the circuit from the ignition switch, terminals 1 and 9, 2 and 4 on the mounting block, 85 and 86 relay contacts, as well as the button itself.

There is no heating of the filaments, but the light in the button works after switching on. In this case, the power to the button is exactly coming, therefore there is a breakdown in the circuit after the switch. It is necessary to check fuse F4, the heating switch on relay and the corresponding terminals in the mounting block, as well as the contacts of the heating threads.

The glass is only partially thawed, indicating that some of the filaments have broken.

Power check

To diagnose an open circuit, you need to know. In direct current (DCV) measurement mode, you need to check sequentially to see if a voltage is being applied to one or the other pins.

To check the power supplied to the relay, it must be removed from the mounting block. To check, you need a multimeter (in constant current mode, up to 20 V) or a test. Turn on the heated rear window. If there is current on the 85 and 86 pins of the relay, then there is a malfunction in the relay itself or in the subsequent elements of the circuit.

To check the performance of the relay itself, it must also be removed from the unit.

You can use the multimeter in resistance measurement or so-called continuity mode. Illumination of different bulbs helps to identify + and -; some devices have a soundtrack.

To check the coil located in the relay, connect the probes to pins 85 and 86. If the multimeter shows infinite resistance, and the red indicator does not light up in the control, indicating a short circuit, then the coil is burnt out or the contacts are unsoldered. For the subsequent check, connect the power supply from the battery to the 85 and 86 pins. After a click, indicating that the coil is working, contact should appear between pins 30 and 87.

If you do not want to test separately the relay and terminals 85, 86 in the mounting block, check if there is voltage at terminals 10 (Ш9) and 5 (Ш8). The presence of voltage will be the fact that the relay and the tracks of the wiring block are fully functional.

If, while searching for a malfunction, you find oxidation of the contacts, clean the surface with sandpaper or a file. The repair of the heater will be completed at this point.

Finding a break in a heating element

There are many ways to detect broken conductive filaments. For searches, you can use the multimeter in resistance measurement mode. You need to measure the resistance at the beginning and end of each strand. The value should be approximately the same. If the value 1 lights up on the screen, this will indicate an open circuit. You can connect to the battery cable leads. The multimeter must be set to DC measurement mode. Attach the positive probe to the positive terminal of the heating element, and apply the negative one to the middle of each thread. The value should be equal to half of the battery charge.

To localize the place, measure in the same way, starting from the edge of the thread. Place the probes at a distance of, for example, 10 cm and work your way to the edge of the thread. In order not to damage the tinting excessively, you can solder the needles to the leads of the probes. This will allow you to discreetly pierce the film without harming the threads themselves.

DIY repair

Rear window heating repair is impossible without a special conductive compound. Special glue can be used to attach the terminals to the element. There are special repair compounds for the restoration of threads. Their cost is quite democratic, and you can find them in almost every department of automotive products. There are also methods for self-manufacturing conductive compounds. Heater repair is as follows:

remove the tint from the break. Use a ruler and a clerical knife to carefully cut the film only along the perimeter of the thread break;
degrease the surface;
stick the masking tape, leaving a place inside for the repair compound;
apply conductive glue;
tear off the tape. Do not wait for the composition to dry, as there is a possibility that the layer from the repair area will subsequently come off along with it.

Do not apply too thick a layer, as this will reduce the resistance and, as a result, the temperature in the repair area.

A heating element repaired in this way will continue to serve you faithfully.

All cars are equipped with a heating system (CO) for the rear window. Thanks to its correct operation, it is easier for the driver to carry out maneuvers, since he will know the situation behind the car. What malfunctions can occur in operation and how to repair the rear window heating with your own hands? Look for answers to these and other questions below.

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Rear window defogger description

So, what is the device for heating the windshield (windscreen) or rear window and what is the purpose of this system? The device is used to thaw ice at subzero temperatures, as well as to remove fogging in wet and dry weather in a car. Special threads are applied to the rear window, which allow you to remove the remaining ice during the warming up of the car in winter. By the way, it is the heater that is considered one of the most effective ways to combat fogging.

A certain number of special conductive filaments on a special film are installed on the rear window. This film is fixed with glue, and the threads themselves are powered by electricity. Electricity passes through the threads, allowing it to generate heat and, accordingly, heat the glass itself.

Working principle and functions

The principle of operation of a car glass heater consists in pressing a button located in the vehicle interior by the driver and further heating the glass. The power itself to the system comes from the positive terminal of the car battery - in this case, the voltage comes through the safety elements and the ignition switch. Ultimately, energy is supplied to the device controller as well as the relay contact. The negative contact of the system is connected to the mass of the vehicle, that is, its body.

When the system is turned on, voltage is applied to the relay coil. When this element is triggered, the contacts are closed, while at the same time two leads are connected, which are marked on the diagram with numbers 30 and 87. Then the energy is transferred to the heating system and fed to the threads, which are fixed on the heated glass with glue. Further, the current again enters through the grounding of the machine and enters the negative video output - Sergey Kotov).

Possible malfunctions and their symptoms

As practice shows, often if the heating system does not work, then car owners will find out about it as a result of fogging up or the appearance of plaque. A person turns on the heating, while there will either be no result at all, or the surface will warm up, but minimally and unevenly. The power supply circuit of the system can be different - in some cars it is activated without turning on the ignition, in others the key in the lock must be turned.

Before checking and repairing the system, we recommend that you familiarize yourself with the list of faults:

The device does not activate. As a rule, there is an indicator on the activation button - if the light does not light up when it is turned on, then the problem must be looked for either in the button itself or in the safety device. In the event that the indicator is on, but the device does not function, then you can also check the relay.
In the event that the CO works, but the glass itself heats up too slowly, which is especially important for the frost period, then perhaps the reason should be sought in the connectors. If the contact is bad, then its resistance may be higher, and the voltage value, respectively, will become lower. As practice shows, often the cause of the malfunction lies in the poor contact of CO with the vehicle's on-board network, so the contacts should also be checked.
Another problem is that horizontal traces remain on the surface of auto glass after CO activation after some time. In this case, the reason, most likely, lies in damage to the threads in certain places. A malfunction of this kind can be determined without testers - just by eye. It should be borne in mind that the threads can break even with minor influences, quite often this happens as a result of using a scraper for scrubbing.

Photogallery "Damaged sections of CO tracks"

Diagnostics and repair

Now more about how to diagnose and restore the damaged area. Let's start by checking.

How do I find a damaged thread?

You can use one of several methods to troubleshoot a problem:

First, you should make a visual diagnosis. If the auto glass is fogged up, then activate the CO. On the damaged area of the surface, fogging will remain after all the other threads have warmed up and the auto glass has sweated. This self-check option is considered one of the simplest.
Also, performance diagnostics can be carried out using a tester - voltmeter. To do this, you first need to turn on the ignition and press the CO activation button. Then one probe of the tester will need to be grounded, that is, connected to the car body, and the other should be wrapped with ordinary food foil, and then brought to the heating track.
When carrying out diagnostics, a voltage value should appear on the voltmeter display, which will be no more than five volts (this is ideal). In the event that the voltage value is near zero or increases to twelve volts, this will indicate that a break has occurred on this track. Thus, it will be necessary to diagnose all tracks.
There is another way to check CO using the same voltmeter. In this case, you will need to connect one contact of the tester to the positive terminal of CO, and the other will need to be moved along the track, only from the side of the negative terminal. In the place where the track is damaged, the voltage value drops sharply to zero.
If you do not have a voltmeter, but you have an ohmmeter, then with such a device you can also check the system. In this case, the tester probes will need to be connected to the negative as well as the positive CO contact. Then you need cotton wool - a small piece you need to moisten in distillate, and then run it along the incandescent path. At that moment, when the arrow on the tester starts to move, you will find a break (the author of the video is Over 9000).

How to make repairs yourself?

If you are faced with the problem of CO inoperability, then you do not have to trust specialists to repair it - you can do everything yourself. There are several methods for CO recovery.

So, how to fix the system:

For repairs, you can purchase a repair kit. As a rule, repair kits for this task have identical parameters and characteristics - with their help, you can restore no more than 10 cm of the damaged section of the track. The repair kit includes directly threads and a balloon with polymer resin. In this case, you will first need to accurately determine the damaged area, for this you can resort to one of the methods described above.
When the place of repair is determined, you need to turn off the CO and remove the film from the auto glass. Then the surface is carefully cleaned and degreased, after which a new track is applied to the damaged area. Using a special brush, which should also be included in the kit, it is necessary to apply polymer resin to the surface, and when it dries, repeat this step again. After completing these steps, you will need to wait at least 24 hours, only after that the CO can be turned on.
Alternatively, to restore the efficiency of CO, you can purchase a special conductive paste. How to restore CO with paste - one layer of it is applied to the damaged section of the track, but keep in mind that in this case you will need to grab the intact thread on both sides by about 2-3 cm.In this case, you will also need to wait at least 24 hours before further operation CO. For faster drying of the paste, the car glass can be blown off with a hairdryer.

The heated rear window of a car often fails. In most cases, it does not fail completely, but in fragments: individual zones or heating threads do not work. In this case, replacing the glass is completely irrational.

There are various ways to self-repair threads and other elements of heating the rear window of a car in order to restore their performance. Let's consider them in this article.

Principle of operation

Heating of the rear window of the car occurs due to the heating of special threads applied to the glass when direct current flows through them. The threads are made of low resistance conductive material. The total current for the rear window defroster is approximately 10 amperes. The number of threads is about ten. Thus, a current of approximately 1 Ampere flows through each strand. It is easy to calculate according to Ohm's law that the resistance of the filament is about 12 ohms.

Heater threads are applied during the technological process of manufacturing the rear window at the factory in several ways:

electrochemical;
vacuum deposition (the most reliable method);
gluing.

The chemical composition of such threads can include various elements, alloys and composite materials: resins, copper, graphite, nickel, chromium, tungsten. The manufacturer does not declare the production technology, therefore, for each technology (heated glass), it is necessary to select the appropriate method of restoring operability.

For example, brazing is practically impossible if the filaments have been vacuum-sprayed with a carbon compound. In this case, only conductive adhesives are effective.

Connection diagram

Typically, the rear window heating filaments are supplied with battery voltage through the fuse, switch and relay systems as shown below.

In some car models, the rear window heating can only be connected when the engine is running. For this, another blocking relay is provided. The fuse installed on the heater supply is usually more than 15 Amps.

Malfunction symptoms

The main signs of a malfunctioning rear window heating:

does not turn on completely;
turns on, but not all threads work (the most common case);
works periodically.

Why the rear window heating does not work: reasons, how to check, finding the place of failure

If the rear window heating stops working or it works, but intermittently, then this may be due to the following reasons:

1. Malfunction of electrical equipment of the car.

The search for the place of failure should begin with the fuse that serves the heater. If it is working properly, then check the switch (button) of the heater, relay, wiring to the heater contacts.

The heated rear window switch button is checked with a multimeter. Its contacts often burn out as a result of the flow of high current. In this case, it must be changed.

One of the most likely places for electrical equipment malfunction is a breakdown (or decay) of the attachment point of the contact terminal to the heater. In this case, repair is difficult. It is required to solder using special solders and flux. Bonding with conductive paste is also possible.

Often the electrical wiring is damaged at the transition point of the corrugation, where the wiring from the body to the tailgate is located. It is required to open the corrugation, extract the wiring, search for the broken conductor and eliminate the breakage.

2. Broken filaments.

Such a malfunction may be associated with the removal of the sunscreen film, mechanical scratches on the glass, and natural wear and tear.

Video - how to check the heated rear window with a multimeter:

To search for a specific place where the thread is broken, if it is invisible to the eye, you must use a multimeter. Its probes should be sharpened or connected to sewing needles. This is necessary to ensure reliable contact of the probes with the heater filaments. First, the faulty thread (s) is identified by a visual or tactile (touch) method. It does not heat up. Then the resistance is measured at the extreme sections of the thread.

After determining the location of the damage to the thread, it must be marked with a marker.

How to fix a heated rear window with your own hands

To repair the heated rear window, you should purchase a special conductive adhesive or ready-made heater repair kits. It is necessary to carefully familiarize yourself with the repair technology, which should be described on the packaging or the attached instructions in Russian. The success of the repair work is determined by strict adherence to the technology specified in the instructions.

Video - DIY repair of rear window heating threads:

Overview of kits and glue for repairing threads and contacts for heated rear window

Permatex PX 09117 set

The set includes:

glue for threads 1.4 ml;
contact glue 0.8 mm;
a brush for applying glue;
sample;
sandpaper;
activator napkin;
alcohol wipe.

Mode of application when repairing contacts:

clean and degrease surfaces;
clean contacts;
wipe the surface with activator, wait 5 minutes;
apply a small (!!!) drop of glue so that it does not protrude beyond the glued surfaces;
press the contacts;
give a day to dry.

Mode of application when repairing threads:

degrease the surface on which the thread will be applied;
attach a template;
wait 20 minutes;
repeat the application 3-4 times at intervals of 20 minutes;
switch on the heater after 24 hours.

The cost of such a set is about 1000 rubles.

Glue AVS A78358S

Such a conductive glue for repairing rear window heating threads 2 ml costs about 200 rubles.

Conductive adhesive for repairing heated rear window threads.

The price of the glue is about 400 rubles.

Video - how to glue the rear window heating contacts without removing the glass:

The repair technology is approximately the same for all industrial adhesives. The main thing is to degrease the surfaces well and not to rush. If you cannot find special repair compounds, you can try to make them yourself or use other recovery methods.

Self-production of conductive glue, soldering with special fluxes, electrolytic coating

1. Self-production of conductive composition.

The widespread glue BF-2 or BF-6 is often chosen as a base. Other quick-drying adhesives can be used. There are options for using polymer resin, paint, enamel. In order to make a conductive paste from these materials, it is necessary to add fine shavings to it in a ratio of 1 to 1. The shavings can be “mined” with a fine file or file and copper, aluminum or brass material. After mixing the components, they are applied to the prepared surface through a homemade stencil. It is not difficult to make it using construction tape or electrical tape.

The effectiveness of such a homemade composition will be no worse than the purchased one.

2. Soldering the point of breaking the thread and disconnecting the terminal.

Soldering of the thread break is impossible if the distance between the ends of the thread is more than two millimeters. In this case, you can first use the electrochemical method. When restoring the contacts of the connection of the heater terminals, the soldering is more efficient and reliable. Soldering is performed using the classical method using active flux and solder. The solder should be POS-18 or similar. It is better to use a flux of the FCA type based on zinc chloride.

3. Electrolytic coating.

To carry out such a coating, a solution of copper sulfate is required (the proportion is 100 milliliters of water, two teaspoons of copper sulfate, you can add a few drops of battery electrolyte), rags, thread, stranded copper wire with a cross section of 6 sq. Mm (for making a prototype of a copper brush).

Next, a copper brush from a stripped conductor wrapped in rags and thread is connected with the opposite end of the wire to the +12 Volt power source (battery), minus the battery is connected to the body or directly to the heater terminal. The brush is moistened with a homemade electrolyte. After that, a moistened brush is vigorously driven in the place of the rupture of the filament. The treatment site is gradually covered by copper particles as a result of the electrolysis process.

Heater wiring diagram

The photo shows a typical diagram for connecting a car rear window heater to the on-board wiring. Let's consider how it works.