Does anyone know the reason as to y the oil pressure gauge in our EF Fairmont is going crazy.

When the car is cold its normal, the needle is pointing to about 3/4 full height. But after about 5 mins its starts dropping until it hits the bottom (red region) and thats when the warning signals starts. But a few beeps, the needle rises back up again. This is a repeating cycle.

The car has gone to the mechanic and they replace the oil pressure send out unit (i dont know the proper name), but the problem remains.

is there any reasonable explanation ??

cheers

have you checked and replaced the oil?

also you can have a bad earthing problem

add an extra eart wire from the battery to the engine block

My au had the same problem and the extra earth wire fixed it!

yes i have had a few with bad earth problem, as engine gets hotter resistance goes up and then the problems start. also have had one that where the oil was air rated which the gauge was working right, put thicker oil in and fixed

MAybe the motors rooted

Just returned from a 800Km trip everything ok untill about 100Km from home when I noticed the oil pressure had gone UP half a notch. Usually sits at 3/4 scale when hot. So I kept a close eye on it for the rest of the trip. It went down to 3/4 again and then back up. It seems to please itself when it does it, not connected to any other changes in the cars speed /revs or anything else. Oil pressure normal at idle only happens at normal running pressure. I suspected that the oil pressure releif valve may have not been seating correctly and now does so occasionally giving the higher pressure..

COMMENTS !!!!!!!!

problem got solved.

discofrank is correct, i added an extra thick grounding wired onto the chassis and to my surprice, it help fixed it.

returned back to normal