The turn signals acting up may actually be a break. Get a schematic and if you have a friend that is good around electrical/electronic things try to get him involved.

There is a strong chance that whatever is plaguing the turn signals is common to the other issues as well. Is this one of the years of the cars with the bio degradable wiring harness? If so it is a suspect.

Apparently the wires in the harness have insulation that breaks totally down. Allowing leakage between conductors . Troubleshooting the turn signals gives a person something to really get their teeth into. You have so much going on cross leakage is a distinct possibility.

Personally after working with schematics for twenty five years I dislike the way some car manufactures do their schematics. Still having one is a real requirement sometimes. Actually if I owned one of the years with a suspect harness. I would look for one of the replacement type on a wreck in the salvage yards. You pretty much know the original type is probably going to fail at some point.

In general yes.

On my 190DT, and probably on your 300D, there's a circuit inside the dome light which allows the interior light to "linger" for a few seconds after you close the door. This circuit frequently fails, leaving no dome light. On the 190DT, I was able to jumper it out of circuit, I'm sure the same can be done on yours with some experimentation. The circuit can't be repaired on the 190, because it's permanently locked into the fixture. The factory repair is to replace the entire dome fixture.

Barry,

From my research, I don't think that this model/year (300D 2.5T, 1992) is part of the biodegradable wiring problem. That said, I just did a visual inspection of the wiring near the connectors on the thermostat. They look good, no degradation. Also, the one wire is blue, rather than a translucent green so it's possible that it's had a replacement harness installed at some point.

I do have a wiring diagram and am looking through it. The bad news is that all of the relevant circuits/components for the turn signals ground through W1 which I have already cleaned/confirmed...

Thanks for you input.