WTB Audi 5000 TD Tach Issue

[Toby]

I am looking for a wiring diagram for an '82 5000 TD that shows the tach wiring. No TD tach wiring in the factory manual, which seems odd. I have no oil light as well. It appears on the gas cars that the tach signal is needed for the magic oil pressure module to function. The car is new to me so I have no idea when this stuff last worked. I just swapped in a rebuilt motor and especially need the oil light to work. I do have pressure and a good switch. I am reluctant to tear into the dash cluster until I have a schemagic diagram unless the problem is in the alternator or attendant wiring.  Any idea where I could find the overheat switch that goes in the back of the head?
TIA
Jason

[R.O.R-2.0]

theres an overheat switch??

[Toby]

Yes, it is the larger of the two senders in the back of the head. It turns on the "Overheating" light on the dash. The small one is the standard VPA temp sensor and it controls the glow plug duration.

[Toby]

So no one here knows anything about VW/Audi diesel tach troubleshooting or has wiring diagram?

[TPW]

Colectb has a Bentley, unless that is what you have already. That engine has two oil pressure senders, one on the lower drivers side of the engine, and the other on the oil pump on the front passenger side of the engine.

[Toby]

I have the factory manual and it has nothing about the tach on a diesel, sad to say. The sender by the oil pump is an oil TEMP sender, not pressure. The oil light needs a tach signal to work the oil pressure module, so no tach, no light.