Oil pressure senders; My limited knowledge

[Lars Arvidsson <arvid@domain.elided>]

Hello to all of you.

I've replaced the oil pressure sender twice on my 75 2.0 TS, and since
I'm uncureable curious,
I dismantled them up.
The first one lasted about 130000 km, The fault was that the linkage
from the membrane to the rheostat arm
had snapped out. No reading at all on the meter.
The second lasted only for a year, it acted kind of wierd, when cold it
raised to 5 bar, and got stuck there.
As heated up, it started to work normally for a while, and then starting
to give far to low readings.
A few weeks later, when I still hadn't replaced it,  the emergency
sender for the oil pressure gave up, then I got
both zero on the meter and a warning light. That was sceary, really.
As I opened it up, I found no obvious cause, some oil on the rheostat,
but a good reading. I tested the performace
when it was dismantled using a tire pump and a ohm-meter. Slightly
heated with a propane torch, the reading
decreased, and the rheostat's arm did move downwards, so it had to be
some problems with the membrane.
But no leakage though...
The one installed right now is also bad, gives low readings when hot.
I've checked the pressure at a garage with a
mechanical meter, and the pressure is fine.
Maybe it's possible to get a discount on the senders if I buy a whole
box of them...?

greetings
Lars  75 Ts 2.0 1990

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