Elusive fuel gauge failure finally fixed

[kragby]

The left tank fuel gauge on my '73 P337G has been inop since purchase two years ago. Mechanic couldn't find the problem. We checked the probes - very simple and nothing much to go wrong there, Sent the control box out for checking and repair if needed. Six hundred dollar repair didn't solve the problem. I removed the top skins and replaced the cabling and redid connections and still didn't work. Finally pulled both probes to check continuity in the cable going through the plate on top of the tank to the probe. On the inboard probe there are four wires coming out the top - two shielded and two reference unshielded wires. The are joined in the potted plastic fitting that goes through the plate and two wires emerge on the tank side that connect to the probe. The shielded cable about a foot long read 10 ohms and should have been zero. I drilled out the plastic piece and put in two new wires - one shielded and the other not. I put in a rubber grommet in the hole and used tank sealer to finish the job. Rewired the connections and that fixed the problem. It was the most unlikely place for a poor connection and the last place I tested but that was the problem.