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Oil Pressure Switch

"Al Powell" <apowell@agcom.tamu.edu> wrote:

The warning light/beeps appear when I start the car and continue when 
it is at idle, as well as while driving it.  Therefore, I presume the 
problem is in the LOW pressure sensor.  Why?
Correct. Open circuit.  

Because if it were the HIGH pressure sensor, no warning should 
appear **until 2500 rpm are exceeded** and the tach interface looks 
for the switch closure in the high pressure module.
Make sense?

The only candidates I can find on my 1990 200 are below spark plug #2 
and behind (top one almost touching) the lower radiator hose...of 
course, in one of the LEAST accessible places on the engine.  The top 
one of these two "suspects" has two connections, leading me to assume 
it's the LOW pressure oil sensor.  One connection would be analog 
gauge, the other the hyperactive idiot light.  The lower sensor 
(immediately below, perhaps 1 inch lower on the block) has only one 
wire, so I assume it must be HIGH pressure.
It's the other way round, Al. The top one - an analogue gauge sender and
a high pressure idiot light.
The bottom  one - a low pressure idiot light.

Igor Kessel
'89 200TQ -- 18psi (TAP)
'98 A4TQ -- nothing to declare
Philadelphia, PA