Hello all,

The ELR (electronic idle speed adjustment) and tachometer on the 1987 300TD are non-op at the moment. All fuses are OK, the plug on the red ELR module on the IP is facing the right way, and the connections are tight and clean. Should I suspect the Klima and/or ELR relay?

I don't know the W124 but I doubt the Klima relay has anything to do with it. I can pull the Klima relay off the SDL (in fact it's out now with a simple compressor relay in its place) and everthing works as it should.

I'd start at the flywheel rpm sensor. Check for an AC signal at pin 2 of the Klima relay connector... or the whichever pin gets the GM+ signal in a W124.

Sixto
95 S420
87 300SDL

Goodness gracious. It must be getting late because my brain doesn't seem to be operating properly. With three 1987 300D's in the driveway, I should just swap ELR relays and associated parts in between cars until I find what the heck is wrong.