After reading the article, "Erratic Temperature Gauge" (February 1977 Roundel) I tried the solution for my fuel gauge but it didn't seem to have any effect.
Still considering it a wiring problem of some sort I hooked the fuel and temperature gauges up separately from the speedometer and tachometer. I proceeded to then test the wires by moving them and I found the faulty wire.
What seems to happen is that the fuel and temperature gauges are wired to a circuit board. These wires are held on by pop rivets. If the rivet does not hold the wire clip tight it will make the fuel gauge jump all over the place.
The solution was to solder the connection to the circuit board and it's working perfectly now. There are only two wires leading from each gauge so it shouldn't be too difficult to find which one is at fault.
And to think the dealer wanted $65 for a new gauge and installation.
Author: John Calabria
Tech. Ed. Note: As we previously said, erratic gauges are caused by poor continuity in the circuit. This includes a poor ground connection on the car, a poor connection at a sending unit, and as Mr. Calabria has found, even at the wire grounding the receiving unit.