There are several things that bear here, don't just easter egg the thing
1...The harness connector pins can break or get loose
2...The IVR "socket" fingers can get corroded and not make contact with the board traces.
3...The gauge stud nuts can work loose, or corrode and lose contact
4...Obviously the IVR can be bad and or the gauges can be bad
5...And......the senders need to have wiring continuity and the senders connected and be good
Here's an old thread on PC board repair
Printed circuit pins repair
Please do not replace the IVR with some mechanical / original device. Look around and find a solid state replacement.
