1990 928 GT oil pressure shows full scale (pegged). but oil pressure is normal

1990 928 GT oil pressure shows full scale (pegged). But oil pressure is normal and variable.

Repair shop wants to rebuild entire wiring harness over this issue. Seems overkill.

Very possibly this could be a failed pressure sender switch (just above the oil filter).   Yours may be a 3 wire switch, they are now available again, I believe - but many have changed to the 2 wire switch and that works fine (have that on my '95).    Lots of discussion about this over the years on the Rennlist 928 Forum.

Gary

I see this problem is in addition to the air bag warning lamp.  I suggest an inspection of the wiring that connects to the instrument cluster (look for corrosion or bad connections) and if no issues are found remove the instrument cluster and inspect for connection issues.  If you can locate a "loaner" instrument cluster to swap see if the problem goes away ... if it does, then you have a faulty instrument cluster.