If you go here and click on the "Relay's and Controls" option you can download the lists and locations of the various relays for the 93-95 E320.

http://mb.auto.pl/index.php/Dok.-serwisowa-CD1.html

Once you find the one listed as "N10 Combination relay (turn/hazard signal,
heated rear window, wiper motor) B.2/1"

Then when you go to figure on page B.2/1 (actually Pg 3) and look for the location of it the designation is H.

"H" (on the diagram on pg 3) happens to be one of the main large Relays in the main Relay box under the hood. The one under the regular fuses.

Interestingly enough I was not aware it also had anything to do with the Windshield Wiper. Once I read this I decided to, when the flashers were malfunctioning, try the wiper. And they indeed did not function, but only on intermittent. They did work on the "full on" setting. Which makes sense in that it must be that this relay only sends impulses like Flashing. However I don't quite understand its role in controlling the rear window defrost. Not even going to try.

So I am going to put in a new relay today and see what happens. Had my Indy pick one up yesterday.

I found no evidence there is anything on the firewall or behind the Speedo and Guage pod so far. Will report results.