Have an '88 5.0L. Battery died, turned it over and it just clicked. Did this a few times and each time the gauges go to their lowest point and it appears they are "under stress" with intermittent power (when it clicks). After I put the new battery in, the oil pressure gauge is not longer reading true. It will hunt from high to very low intermittently. I changed the sending unit, oil filter etc no change/improvement. I hooked up a mechanical oil pressure gauge and there's lots of pressure and it's steady as a rock. The solid oil pressure isn't a surprise as this is a very original low mile car that's never been driven hard. I'm confident I did something to the gauge when I turned the car over with a dead battery. My question is how to best fix this? Do I just swap out the gauge or is there another fix?
Easy to test the gauge.
1. Remove the wire from the sender.
2. Turn ignition on.
3. Read gauge. It will be either be all the way to the top or all the way to the bottom.
4. Ground sender wire. Gauge will swing to the opposite direction.
5. If it does all this, gauge is good.
6. If not, it could be the wire to the gauge or the sender.