'88 TQC intermittent oil pressure warning

[sevans@radstone.co.uk (Steve Evans)]

I've owned an '88 Coupe Quattro Turbo (2226cc 10V) for a couple of months and
on four occasions (that I'm aware of), have had the oil pressure light come on
briefly and then promptly go out again. Whenever this has happened I have
checked that the oil temperature and that the engine temperature are OK and
the readings are normal. On other occasions after doing 90 mph for a couple of
hours on the motorway, with the oil temperature reading somewhat higher, I have
never had a problem, so I don't think there is a real problem with the engine.
The owners manual states that there is a warning buzzer associated with the
oil pressure warning light yet this never sounds (except for a "ping" sometimes
when I first turn the key in the ignition).

I'm trying to figure out what the problem could be (without spending a fortune
at the local Audi delaer). I have a few ideas - any comments.

1. Dodgy sender. Are these a known source of problems?

2. Loose/shorting wiring associated with the warning circuit.

3. Sticking oil pressure relief valve. Can this be replaced with the oil pump
   in situ - is the plunger available separately from the oil pump?

Apart from these worrying warnings the car goes like a dream and is perfect
for wet winding country roads.

Regards,

Steve Evans
'83 Triumph TR8
'88 Audi Quattro Coupe Turbo