Homemade gauge test tool, C-3826

67Dart273 said
There are many threads on these issues. Some of them are

1....broken/ loose harness connector pins at the PC board. Clean them and solder them to the board traces

2...Ditto the contact fingers for the IVR (instrument voltage limiter) Solder jumpers from the contact fingers to the board traces

3...Poor connections at the gauges studs. Loosen/ tighten the nuts several times to "scrub" the connectors clean, and consider replacing the nuts

4...Flakey / bad IVR replace with a commercial solid state replacement or google search one of the many DIY circuits

5...Add a grounding pigtail to a common point on the cluster and bolt it to the dash frame/ column support

6...Don't discount poor connections in the power circuit feeding the cluster, or to bad connections leading to the senders. This includes the left kick panel connector (tail harness gas tank sender) and the bulkhead connector (temp sender and oil if used) as well as poor connections at the senders that is the wire end itself.

And then of course the gauge units themselves can be bad

I’d be willing to bet money the gauges themselves are fine, and the issue is one or all of the above. My gas tank leaks when filled above 3/4 full, and I believe that stems from a bad gasket where the filler neck meets the tank, and as such haven’t messed with the tank sending unit as It’s no use until that leak is resolved.

The wiring being bad somewhere along the way wouldn’t surprise me in the least. The previous owner took the car to a mechanic who butchered the wiring. Completely bypassed the fuseblock, wired things in strange places, and just spliced and taped wires left and right. I’m planning on replacing my underdash harness with a totally new one with a blade fuseblock, and hope to get into all sorted out, which will hopefully fix my gauges. It’s possible when he was messing around, he connected things wrong.