car: audi 80 2.0ltr 16v 1991
can anyone tell me what it means when the oil light comes on and beeps at
the same time, i have tried shorting the oil pressure switches to earth
which activates the oil light, but no beep, there is plenty of oil in the
engine so i'm figguring it cant be a low level warning lamp.
it tends to come on and beep at about 2500 rpm.
any advice welcome.
In brief: get the pressure checked as soon as possible. I had a
similar problem and wrecked my engine by not taking it serious.
What happened was the following (from memory, I might confuse the
The Audi 100, 1989 I have has two pressure switches, one is closed at
no pressure and opens at ~0.3 bar , the other one open at no pressure
and closes at ~1.8 bar. The auto-check system checks both, but at low
refs only gives a warning when the pressure is below 0.3 bar. It only
checks the second switch at somewhere around 2800 rpm. It also checks
the switches when the engine is not running and gives a warning if
they don't show zero pressure.
On mine, the low-pressure switch had bad contacts, so that it was
always "open". I think it had around 10 Ohm when "closed", but that
was enough for the auto-check to regard it as open. It always gave a
warning when I turned the ignition before I started the engine, but
since I was used to have the oil lamp on before the engine starts, I
didn't pay attention (it was already like this when I got the car).
Therefore, the system never detected a fault on the 0.3bar switch. At
some stage, I got oil warnings at around 100km/h. When I reduced the
speed, the warning was gone again. That was basically the 1.8bar
switch. The problem disappeared again and came back half a year later.
By the time I got a proper pressure check, it was too late.
- If the autocheck system gives you a warning before you start the
engine, one of the switches might be faulty.
- Put a DMM on the switch to measure resistance. One of the should
change immediately when you start the engine. The other one should
change before you reach 2500 rpm, better much lower.
- Replace the switches, if they don't change properly.
- I would say have the pressure check, if in any doubt.
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