Okay, I'm pretty sure I have a problem in my OVP / ELR circuitry which is causing a weird set of problems.

Frequently (but not every time) I start my car (an '87 190D 2.5T driveline transplanted into a '93 190E body), I get a condition where my tach does not function, and I can tell the idle speed is low. When this condition occurs, my A/C compressor will not engage, either.

I checked my Electric Troubleshooting Manual, and it seems that all of these circuits are tied to the ELR / OVP.

The strange part is that after a few minutes, the engine will often have a quick "sneeze", followed by the tach starting to work, the idle picking up, and the A/C compressor being allowed to work. Everything is fine after that.

Does this sound like an OVP relay problem? Perhaps the relay just isn't pulling in, gettting "stuck" in the open position until the right set of conditions (heat, vibration, etc) are met?

Could the problem actually be in the ELR adjustment pod? Is there a way to test the pod independently of the OVP?

Any advice on this issue would be appreciated.

SteveM.

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'93 190E/D 2.5 Turbodiesel 5-speed (daily driver)
'87 190D 2.5 Turbo rustbucket - parts car
'84 Dodge Rampage diesel - Land Speed Record Holder
'13 Ram 2500 Diesel
'05 Toyota 4Runner