My son's 1990 240 sedan turned up with a failure of the rear window defrost and winter is bearing down on us here in Ohio... (I know - not as bad as New England but still bad enough where defroster is valuable)

Light won't turn on and no heat coming from the filaments (?) in the rear window.

I've cleaned the two fuse holders (11 and 12) and replaced both fuses with new ones, I've swapped the switch with a known good one with no luck... so I think what I'm left with is the relay... I have a what I believe is a good spare relay and I found an empty socket that that relay fits into (up under the instrument panel) but that didn't turn it on either so maybe that empty socket is for something that I don't have in that sedan??

I've searched through the archives and found Art mentioning the location of the relay (under the metal plate below the carpet at the left Drivers foot postion). He and others noted they had never heard of a failed rear heated window relay. I took that plate off and there were no relays under there.. just wire harnesses.

Would anyone be willing to hazard some thoughts to this bad shade tree mechanic who regularly fails in his troubleshooting attempts?

thanks!

Jack
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Bad Blue - '86 245 with 303,000 mi. (now for parts), Good Green 1990 245 with 178,000 mi., Blacky - '91 740 wagon with 180,000 mi., Mean Green - '94 850 with 222,000