W126 Rear Defroster Not Working

[Marshy]

Hello All!

I have a 1985 500 SEC. The rear window defroster is not working.

Diagnosis:

When I push the button on the center tower, the light comes on and I can hear the relay click under the driver side dash. The interior light does not dim. Does this mean I have power to the switch and in turn to the relay.

When I release my finger from the dash button, the button returns to the neutral position and the light goes out. Does this mean that the relay isn't "holding"? I suspect that the relay has a timer where it latches (holds) the circuit closed for 15 minutes or so before releasing.

I have tried holding the button in manually for a few minutes. The rear window does not defrost.

Anyone been there and done this?

Thanks for any suggestions.

Dave in Ontario, Canada. -5C and snowing.