Defogger

The rear window heating is a standard equipment of a motor vehicle. It is installed as standard in almost all passenger cars and was developed in the early 1960s by Heinz Kunert.

Legal regulation

In Germany it is indirectly required by § 35a para 2 traffic regulations: " For the driver an adequate field of vision must be guaranteed under all operating and weather conditions. "

Design and function

The electric rear window heating may ( at least ) can be realized in two ways. Firstly, the heating wires can be printed from within the disc, which is a low-cost variant produced. Here are the heating cables through the oxide layer usually red and about 1 to 2 mm thick and are perceived by some as disturbing. Also, they are unprotected from damage caused by sharp or sharp objects in the car. They can be repaired but - since they are freely accessible.

Another variant of the heated rear window is not imprint the wires, but introduce actual wires between the two layers of a laminated glass pane. These can be much thinner than 1 mm here and are therefore less visually distracting. A disadvantage is the high production costs and therefore the high price of such a disk. Also, it can not repair a damaged due to aging heating wire, as it is indeed between two slices. Against damage from lace or sharp inside the wires but are protected.

The rear window defogger in the variant " wire between two laminated glass, " appeared in January 1964 for the first time as code 248 in the charge lists of Daimler -Benz AG. On Oldtimertreffen one gets occasionally to see such a heated rear window today.

The rear window defogger in the variant " printed circuit traces " was developed in the late 1960s at the Ford Motor Company. In 1974 she was first fitted as standard in the Lincoln brand vehicles. It consists of thin electric heating cables, which are applied to the inside of the rear window. Switching on the rear window heater current flows through it, causing them to heat up due to the electrical resistance. This icing or fogging caused by moving the local dew point on the disk is avoided. On some vehicles, the heating conductors serve as an antenna for the radio. Damaged areas or breaks in the heating conductors may cause harmful interference to radio with activated rear window defogger.

If a printed heating is interrupted, repair by coating with silver powder suspended therein ( conductive paint ) is possible.

The power is supplied from the electrical system. An average rear window heater has a power of about 150W. Continued operation of the rear window heater is connected to a fuel consumption of about 0.13 liters per 100 kilometers, as the alternator has to provide higher performance. For this reason, many rear window heaters have a timed shut-off.

Literature

• Rudolf Hüppen, Dieter Korp: Auto electrics all types. 7th edition, engine book publishing house, Stuttgart 1972, ISBN 3-87943-059-4