[balmfort]

Just changed my oil & filter on my 1963 GP (389). It has the original oil warning light still wired in but I have a separate electric oil pressure gauge. Warning light comes on but I have great oil pressure and no visible signs of leaks. Any ideas, maybe bad ground in the dash circuit?

[george kujanski]

Or a ground on the wire to the oil pressure switch. Does the electrical OP gauge work correctly, i.e. zero with engine not running, reading higher when cold, etc.?

George

[Bill Hanlon]

The lamp has 12volts on one side any time the key is on. The other side goes to the sensor which provides a ground any time the oil pressure is below a small set amount, turning on the light. If the gauge is reading suitable pressure one of two things have happened.

1. The sensor has failed. With the key off, pull the wire off the sensor. Start the engine. Does the light come on? No = a bad sensor.
2. Something is providing a ground for the lamp other than the sensor. That will take some troubleshooting.

[balmfort]

yes, electrical gauge (Stewart Warner) seems ok, 0 psi engine off, 60 engine on cold. Im thinking its a bad oil pressure switch

[SRGN]

I recently had to fix a similar issue on a friend's car, his son helped him change the oil and managed to pinch the sending unit wire in the oil filter. He couldn't even get mad since the kid(11 years old) was really trying to learn. Anyway, do as posted above and unplug the sending unit. If the light stays on with the switch unplugged, it's likely a wire with worn insulation grounding out and causing the issue.

[Goatracer1]

If the light worked before changing the oil remove the sensor. Pull the coil wire and have someone crank while you watch and see if any oil comes out of the hole the sensor screws into. Something could have blocked the hole.