sunpro electronic oil pressure gauge doesnt like 12v :/

[Kozworth]

I got a sunpro oil gauge, I have put it in a tee to the stock oil sender spot. I got both the oem wire and a new wire going to the sunpro sender. The new wire goes to the S on the gauge, and then reads ~20psi. When I put 12v from the power distribution block to the + on the gauge, and ground the gauge to the strut tower the oil pressure gauge reads zero.

I have a sunpro voltmeter, which both the power and ground to the voltmeter are the same as the oil pressure gauge, and when I connect ground the voltmeter reads 12v but the oil pressure drops to zero. When I disconnect ground, the volt meter drops to 0v but the oil pressure reads ~20psi. This has happened on two different senders.

Any reason this is happening? How reliable is the gauge reading 20psi, or is it just being funky? Any issues just leaving 12v off the oil pressure gauge and calling it a day? Havent had the car running yet enough to see if the gauge changes, nor do I want to because I do not want to risk eating up my fresh rebuild.

[jlevie]

I've not used one of those gauges, but most of the electrical oil pressure senders have a single lug for the signal wire. If I understand correctly, you have the signal wire and the original oil pressure switch wire connected there. Which is wrong and will cause incorrect readings. Only connect the wire from the gauge to the sender.

[Kozworth]

I see, I figured if I connected the oem wire as well then I would not get a low pressure light. I will try removing the oem, and still applying 12v to see how that changes.

[nando]

if you leave the OEM wire disconnected the light will stay off - it only completes the circuit to turn on the light when the pressure drops too far, otherwise the circuit stays open.