ur-quattro oil temperature problem

["Dave Eaton" <Dave.Eaton@clear.net.nz>]

as some know, i've been chasing an oil temp problem in the ur-quattro.  170c
indicated after a "moderate" run with water temperatures warm, but not hot.

1) gauge checks out ok.

2) i replaced the oil temp thermostat (2 months wait for the parts from
germany).  access from the bottom is the go here.  no difference to the
symptoms.  mmmm

3) further testing strongly suggests the possibility of a voltage drop in
the system leading to the oil temperature gauge going skywards e.g. the oil
temperature is higher with the beams on high than on dipped, turn off the
lights, and the oil temperature gauge drops 3 segments.

anyone seen anything like this, and have any additional comments?

regards,
dave
'95 rs2
'90 ur-q
'88 mb 2.3-16