While driving the other day my oil pressure went from 40 down to 12 pounds. I turned off the motor and the gauge went to 0 like normal. I recrank the motor and it goes to 12 pounds. I rev up the motor and no mater how high I push the RPMs, still only 12/13 pounds. The car runs fine. No clatter, no lifter noise at all. I've tried 2 new oil pressure switches. First one didn't show any pressure, I took it back and got another one. It showed ever less than the original one. I put the original one back in. Is there a way to test the pressure switch to make sure if it's good or bad? any input would be greatly appreciated!!!

 

There's no way with your engine since you don't know if it's the engine or not.

There is no easy way with the sensor out of the engine. The sensor is a variable resistor so you have to connect an ohmmeter and then apply pressure to see if the resistance changes. You also have to find the the specification table listing pressure vs resistance to check against.

Best is to connect a cheap mechanical gauge to confirm the oil pressure is good. Then try fixing the gauge once you know the engine is OK.

 

I agree.. about the only way you'll know is to replace the sender. You can pull an ohms reading off the sender and see if it's working but without a mechanical gauge in line you'll just be guessing. The oil pressure gauge works just the same as a fuel gauge only the oil dampening fluid is not as thick in a oil pressure gauge (more responsive). So... 0 is 0, 45 ohms is 40 lbs, and 90 ohms is full at 80 lbs..

You can test the dash unit by pulling the ohms wire off the gauge. The gauge should peg... Then ground it out and it should go to zero.

Willcox