Both of my pressure gauges (oil and fuel) are reading low (about half). We (my A&P and I) put a mechanical gauge in the circuit and verified the electrical gauge readings are low. We've checked wiring connections, power and ground. I've checked the sending units and not sure the resistance is correct. The sending units doesn't appear to be the original ones. I'm concerned that they may have been replaced with the wrong resistance units.
The fuel pressure gauge is 0-30psi
The oil pressure gauge is 0-100psi
Can someone tell me:
1) What should be the resistance ranges of the sending units?
2) What should be the voltage on the wire with it disconnected from the sending unit? I'm reading about 2 vdc.
This is a new plane to me and I have the service manuals ordered but haven't received them yet.
Any help or ideas are welcomed!