I am having problems with the rear window defogger on my 94 E420. When I push the switch to turn on the defogger, the indicator lamp lights up, but does not stay on when I let go. It seems to me that it can only be one of two possibilities, either the switch or the relay which controls how long the defogger stays on. My money is on the relay, since the indicator lamp lights up when I push the switch. If it is the relay, can anyone please tell me where it is located? If there is another possibility, I am always grateful for any thoughtful response. Thanks.

Also could be a FUSE! Take a look at #1 & #10.

I should have noted in my initial post that maybe once out of fifty times I check it, it seems to work. I looked at the fuses, and although I cannot say that I was completely familiar with that type of fuse, they appeared to be okay in comparison to the spares in the fuse box. Are the relays in the sealed black enclosure immediately behind the fuse box? It looks to have 3-4 screws holding it closed. If not, where are the relays? I ordered a used relay from SilverStarRecycling for $35 (better than the $145 quoted from the dealer), hoping that it would do the trick.

If anyone has any other suggestions, I am all ears.

With this style of fuse ALWAYS remove it & reinstall after cleaning contact area!