I have a 1988 mercury tracer, and the rear window defroster is not working. I have checked the switch and it seems to be working by having the indicator on the dash light up when it is turned on. There is reference to a relay timer for the switch. Does anyone know where the relay is located, or if it is part of the switch assembly?

Can you post the wiring the diagram

Upon checking more, I did find a relay on the firewall under the hood that clicked each time I turned the switch on and off. The other thing I noticed is that there was two lines (assumed to be vacuum) leading form the relay to the engine. Two wires running to the relay. With the switch turned on, one would have power (checked with a light). When turned off, the second would have about 1/2 the power (as shown by the light). Does this make any sence? Is there a problem with this relay under the hood, or may it be a problem with the switch in the car?

its most likely your relay, wiring to the window and the window grid itself.

To test the grid take a DVOM and measure the resistance of all the grid.

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1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)