Checking the rear window defroster (Mercedes-Benz E-Class W210)

The rear window defroster circuit is protected by fuse #19 in the fuse box next to the battery and receives voltage when the contact of the corresponding relay in the combination relay is closed. This occurs when the switch located on the instrument panel is pressed (the control lamp lights up), and only if the voltage in the on-board network exceeds 11 V. Control is provided by the electronics of the combination relay. If the ignition was turned off while the rear window heater was on, the heater must be turned on again. If the window heater does not work, proceed as follows.

Sequence of works

1. Check fuse #19.

2. Remove the trim of the right and left rear pillars from the latches. Approximately 20 cm from the lower corners on each side are the contact connectors.

3. Check the reliability of these connectors. If there is voltage on the black wire, but the glass does not heat up, there is no contact with the "ground". Check the connector and wiring.

4. Remove the two-position heater switch from the instrument panel and use a tester to check for voltage on the black-yellow-green wire when the ignition is on. Is voltage supplied to the black wire when the switch is turned on?



5. Check if voltage is supplied to the relay from contact "30" to contact "87". To do this, remove the relay and install a jumper. If the heater starts working, the combi-relay is faulty. Replace the combi-relay or install an additional separate relay in the heater circuit.

6. If the heater wires are damaged by sharp objects on the rear shelf (for example, if only some of them work), for repairs you can use conductive silver varnish, for example Doduco brand (available for retail sale).