Pic. 10.11. Scheme of switching on the rear window heating element: 1 - mounting block; 2 – an element of heating of back glass; 3 – the switch of heating of back glass; 4 - switch (lock) ignition; 5 - main fuse box; A - to the electrical package control unit, terminal «10»; B - to the lighting control module (instrument lighting controller), terminal «58b»; C - to the terminal «plus» battery; K4 - additional relay (ignition relay); K2 - rear window heating relay
The scheme of system of heating of back glass is resulted on fig. 10.11.
The rear window heating element is switched on using the K2 relay installed in the mounting block.
To prevent the battery from being discharged by a heating element left on when the engine is not running, the heating can only be turned on when the ignition is on. To do this, power is supplied to switch 3 through an additional relay (ignition relay) K4, triggered when the ignition is turned on, and fuse F11. Power is supplied to the heating element through fuse F2 in the mounting block located in the passenger compartment.
If the tailgate glass is not heated when the heating is turned on, check fuse F2 and F11 in the mounting block, fuse F2 in the main fuse box, wires and their connections, switch and relay K2.
If all fuses, relays, and heater element power circuit are good, check the conductive strips for damage.
The check is carried out with the engine running and the heated rear window turned on. Measure the voltage on all strips one by one with a voltmeter, connecting one lead of the voltmeter to «mass» body, and the other in series to the conductive strips. If the voltage measured by the voltmeter at the beginning and end of the strips is the same and approximately equal to the battery voltage, check the reliability of the contact «mass» heating element wires with car body.
The voltage on the strip should decrease as the voltmeter connection is removed from the positive polarity bus of the element. The voltage must be measured at least in two places at the same distance from the axis of symmetry in order to exclude the possibility of missing a damaged area. If you find a discrepancy in the readings on one of the strips, move the voltmeter wire lead along this strip until the voltage becomes zero. A sharp decrease in voltage indicates a strip break at this point. Mark on the outer surface of the glass with chalk or a glass grapher the place of the break for the subsequent repair of the damaged area.
To repair the heating element, you can use one of the commercially available special kits, which include silver. Despite the fact that the kits are made by different manufacturers, their composition is approximately the same, all kits are supplied with instructions for use. The following is a typical workflow for these sets.
1. Remove a 6 mm strip from each side of the damaged area.
2. Wipe the damaged area with a clean cloth dampened with alcohol.
3. Stick repair adhesive tape or two pieces of ordinary adhesive tape on the glass at the point of damage to the strip at the top and bottom of the repaired area, and the distance between the pieces of adhesive tape should correspond to the width of the conductive strip on the glass.
4. Thoroughly mix hardener with silver base compound. If the hardener has thickened, place the package with it in hot water and wait until the hardener becomes liquid.
5. Apply the composition to the area to be repaired with a wooden spatula and remove the adhesive tape.
6. Install the heater at a distance of 25 mm from the damaged area and heat the composition for 1-2 minutes. The minimum heating temperature is 149°C.
Note. In some kits, the composition does not need to be heated: it polymerizes at room temperature.
7. If the strip becomes discolored after drying, apply a tinting iodine composition on it with a brush - the color of the strip will be restored. After the iodine compound has dried for 30 seconds, wipe off any excess with a clean, lint-free cloth. During the polymerization of the repair composition, which lasts 24 hours, exclude any mechanical impact on the repaired section of the strip.
8. Turn on and check the operation of the rear window heating element.
If the wire has come off the bus, solder it with solder containing 3% silver and rosin paste as a flux in the following order.
1. Clean the solder area on the busbar and the wire strand.
2. With a brush, apply a little rosin paste to the connected places of the wires and tires.
3. Apply a thin layer of solder to the wire strand.
4. Solder the wire to the bus, avoiding overheating of the connected parts.