'90 300E electrical issue. Looking for help/parts

[Andy_M]

Yesterday I took my 90 300E through the car wash to get the salt and calcium off. All was just fine before and immediately after the car wash. But a few hours later, after shutting the car off for an hour or so, when it was restarted the following happened about half way to work:

1) Bulb out warning light went on.

2) Noticed that dash lights are either out or VERY, VERY dim. It was still daylight enough that it was hard to tell which was the case. Couldn't check them in the dark last night because I was working, but honestly, I think they are out.

3) Rear right side tail/stop/side marker assy seems dead. nothing is working. This side has a ground wire, attached to the wiring at the connector and grounded to the chassis just below the light assy, which doesn't appear to me to be stock. PO may have had to add this ground for some reason.

4) Have had trouble with this R side assy blowing bulbs periodically ever since we bought the car 4 years ago.

Fuses have been checked and appear fine. Bulbs appear to be fine. Checked that odd ground wire and it does not appear loose or to be making poor contact. Wiggling the harness and the ground wire netted no response at all. Do not see anything that is obviously wet, but I will stop short of saying conclusively that nothing is wet.

Other than the obvious hunting with a meter, anyone familiar with this scenerio and have an idea what to look for?

ALSO: I don't know where this rear harness ends, but does any one have either a full trunk area harness in good shape, or a pigtail clip for that right side that I could buy off you reasonably ?