Oil warning light and buzzer comes on intermittently

[volkswagen 1200]

I have a 1993 Audi V8 with 50,000 miles which has an oil pressure gauge and oil temperature gauge. The gauge reads almost maximum and the oil temperature reads low all of the time. The pressure increases slightly with the revs which is normal. A new Audi oil pressure sensor has been fitted to the engine in the last few months.

The oil warning light comes on and the buzzer goes off intermittently and I believe it is a problem with the diagnostics of the car rather than any oil related problem with the car.

Can anyone tell me which oil senders or sensors need replacing in order to eradicate the problem.

I have owned a Audi 100 in the past from new which had the same problem but I sold the car when Audi would not fix the new sensors for free - this meaning I never did find out which sensors were at fault (Audi at the time confirmed that the problem was caused by faulty sensors on the engine).

[volkswagen 1200]

I have a 1993 Audi V8 with 50,000 miles which has an oil pressure gauge and oil temperature gauge. The gauge reads almost maximum and the oil temperature reads low all of the time. The pressure increases slightly with the revs which is normal. A new Audi oil pressure sensor has been fitted to the engine in the last few months.

The oil warning light comes on and the buzzer goes off intermittently and I believe it is a problem with the diagnostics of the car rather than any oil related problem with the car.

Can anyone tell me which oil senders or sensors need replacing in order to eradicate the problem.

I have owned a Audi 100 in the past from new which had the same problem but I sold the car when Audi would not fix the new sensors for free - this meaning I never did find out which sensors were at fault (Audi at the time confirmed that the problem was caused by faulty sensors on the engine).

I have found that I can make the oil pressure sensor go off by closing the bonnet on the car with a thud. As the bonnet is slammed closed the oil warning buzzer sounds. This makes me think that there is a faulty connection or printed circuit.

1. Am I right in thinking that there could be a faulty connection or printed circuit or could there be another oil sender on the engine which is faulty (if a vibration is something that can show up a fault in a sender)?

2. In terms of the electrical circuit where would the problems connections be in the Audi 100 (C3) and what should I look for?

[scotty33]

I dont know if the same applies to the V8, but generally VAG cars of the era have 2 oil pressure switches. One which reads minimum oil pressure at idle and would go off at approx 0.5 - 1 bar. The other sender needs to 'see' above approx 1.8 bar at 2000 rpm. If the alarm occurs below 2000 rpm, then it concerns the lower pressure switch.
I have seen damaged engine earth wiring cause oil level alarm problems. If there are a bunch of brown wires connected to a stud on the intake manifold, make sure the wiring is not chafed or breaking down. Engine movement can cause the strands to break where the lug is crimped on. Same goes for the wires to the sensors.
Most Audis with the oil temp gauge, rarely register much movement,

[volkswagen 1200]

I dont know if the same applies to the V8, but generally VAG cars of the era have 2 oil pressure switches. One which reads minimum oil pressure at idle and would go off at approx 0.5 - 1 bar. The other sender needs to 'see' above approx 1.8 bar at 2000 rpm. If the alarm occurs below 2000 rpm, then it concerns the lower pressure switch.
I have seen damaged engine earth wiring cause oil level alarm problems. If there are a bunch of brown wires connected to a stud on the intake manifold, make sure the wiring is not chafed or breaking down. Engine movement can cause the strands to break where the lug is crimped on. Same goes for the wires to the sensors.
Most Audis with the oil temp gauge, rarely register much movement,

Thank you for the very helpful email. My car has the two oil pressure sensors plus an oil temperature gauge.

1. Where would the gauge which reads the minimum oil pressure be located on the engine? I have replaced the sender for the high oil pressure and nothing appeared wrong with wiring for it when I was replacing it.

2. 'Most Audis with the oil temp gauge, rarely register much movement' Do you mean that an engine with the Temperature Gauge fitted moves less, why would this be the case?

3. I am going to check the engine earthing also. What am I looking for in the busy engine bay?

[scotty33]

Sorry, my bad terminology!

1 there are 2 oil pressure switches, low and high pressure either of which can cause the buzzer and warning light (under the conitions described)
Typically 1 of them may be mounted on the oil filter mounting, but could be anywhere on the engine block tapped into the lubrication system

2 all I mean is that the range on the gauge seems unsuited to use in the real world. The only time the temperature gauge needle rises seems to be under sustained high speed use eg a trackday.

3 My 20v has a group of 3 or 4 small gauge wires (<2mm cross section)with brown insulation these terminate in a connector with an 'eye' which is fitted to a 6mm stud on the rear of the inlet manifold. 2 of mine were damaged and my car was intermittently throwing oil level alarms on the autocheck and misfiring which developed into a full cut out. I don't know that one of these earths would be for the pressure warning system, but may be worth checking?