'89 560SL tail light

[rjk]

Pass side tail light does not glow
Looks like a poor connection somewhere between the fuse box (full 12V @ fuse #13) and the rear wiring harness (3-5V)
There is only 3-5V everywhere I can test it in the trunk area (measured at the gray/red wire along the right quarter, 8-pole connector & bulb socket)
Wiring diag. shows a 12 pole connector upstream of the trunk
Is this connector in the rear of the car, midships or under the dash?
Or is it likely the bulb-out sensor solder joints need to be reflowed, is that under the dash?

As a side note, the pass. side taill connector shows 12V at pole #7 which the wiring diag. claims is not connected as of MY 86. No revisions shown in Startek.
Anything I am missing?

[Diseasel300]

Does the R107 even have a bulb failure module in it? If you're only getting partial voltage at all of your pins in the same plug, I'd suspect a bad ground. If you have access to the factory service manual, it will give a connector name for the 12 pole connector you mention. The end of the ETM should have a reference section telling you where the various connectors are in the chassis.

[rjk]

I'll check the wiring diag. again but first I looked, it only mentioned the wire going to a 12 pole connector between the tail light and the failure sensor.
Yes, the 107 has a bulb failure sensor, just not sure where it is but think it is under the dash behind the glove box.
Partial voltage is only on Pin 6 all the rest show a full 12V so it isn't the ground.

[Diseasel300]

If you have a bulb failure module, they're known for getting cracks and breaks in the solder joints on the circuit cards. My '83 hasn't got one, I didn't know if the '86+ models did or not. Not sure where it is, but it's worth pulling and inspecting/resoldering the solder joints where the pins meet the card.

[97 SL320]

Where are you picking up your test ground? If from the tail light system, a bad ground will affect everything. For situations like this, I tend to add a temp ground / apply power to circuits as a test.