Oi pressure gauge sensor

[RubbishFettler]

Hi All

The oil pressure sensors have been disconnected while doing work on the car, including fitting new oil pump gears. I have reconnected them, but when I have gone to start the car, the oil pressure gauge needle goes straight to maximum.I just wondered if it is possible that I have got the wires the wrong way round.If I have, would this produce the result I have got, or could something else cause the gauge to read incorrectly? Any advice appreciated, as always.

Cheers

Steve

[KKson]

You have put the wires back the right way? i.e. pressure transmitter and pressure switch? I may be talking bo***cks but I'm assuming that if the pressure gauge was wired to the switch then this would give full scale deflection?

Worth double checking. On mine there is only one wire to the pressure transmitter so no way of wiring it incorrectly.

[RubbishFettler]

It's not impossible as the wires look the same colour. If that was the case, how would it affect the oil warning light?

[KKson]

RubbishFettler said:

It's not impossible as the wires look the same colour. If that was the case, how would it affect the oil warning light?

I'm guessing that if there's pressure then a circuit will be created which turns the oil warning light off. With no engine running there is no circuit (i.e. no oil pressure) then light is on.

[ElvisWedgely]

KKson said:

RubbishFettler said:

It's not impossible as the wires look the same colour. If that was the case, how would it affect the oil warning light?

I'm guessing that if there's pressure then a circuit will be created which turns the oil warning light off. With no engine running there is no circuit (i.e. no oil pressure) then light is on.

Keith is right in saying that a circuit is created to turn the light off. In actual fact the circuit is broken to turn the light off. The switch on the engine is self earthed and when pressurised breaks the circuit to the live wire.

The pressure gauge works in much the same way, only the pressure sensor switch on the pressure gauge on the engine block is of a different type to the pressure light. On this, the sensor gives a varying level of earth to the live wire from the gauge hence giving a reading.

If your oil pressure gauge shoots straight to the maximum position, you either have a shorting of the live wire connected to it directly to the earth or the pressure sensor unit is knackered and is earthing straight to the engine block.

To test either one of the oil switches, turn the ignition on and touch the wire behind it to the engine block. If the gauge shoots straight up you know the gauge works fine. Same with the light. If the light comes on you know the bulb is fine so either the switches or the way they are earthed to the block would be at fault.

So to answer your question of swapped wires, yes the gauge would go to the maximum because the oil light sensor switch is already on full earth and only operates by breaking circuit when pressurised and turns the light off. It is possible that you may have put them on the wrong way.

ps. don't short out the live wire of the gauge to earth for too long as it could damage the gauge. Just a quick touch to earth would confirm whether it works or not.

The advice given above is in good faith for information purposes and no responsibility is accepted.

Tony. TCB.

Edited by ElvisWedgely on Thursday 3rd March 14:20

Edited by ElvisWedgely on Thursday 3rd March 14:27

[RubbishFettler]

Thanks for that fellas. Turned out I did have the wires crossed, wouldn't you have thought they would be different colours. Cracked her up and all seems well in garage world- what did we do before Pistonheads?

Steve

[adam quantrill]

Even if they start off different colours they usually end up black and gungey both.