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Re: 85 dual tank gage question
Quote:
Originally Posted by hatzie
A & C come off the tank senders to the switched contacts of the SPDT switch inside the valve.
B is the common terminal on the gauge switch inside the valve and the B wire terminates to a molded rubber disconnect on the RH frame rail. The wire runs from there up to the bulkhead plug under the brake booster.
Honestly it's usually not difficult to diagnose and fix the fuel gauge in the dash.
The tank ground wire is one of the more common failure points in the 1973-1986 fuel gauge circuit. It either gets left off by someone replacing the tank or the wire rots off the ring terminal at the frame or the .250" disconnect on the sender locking ring rots off the wire.
If the stock fuel gauge is nailed at 3:00 you likely have a bad tank ground wire.
Easy to test and not awful to correct. Take a set of jumper cables and attach one end to the frame and the other to the pinch weld on the selected fuel tank. If the fuel gauge needle suddenly comes to life with the KOEO (key on engine off) you'll need to fix the tank ground wire between the frame and the sender locking ring. Many moons ago I attached an alligator clip jumper wire from the frame to the pinch weld on the tank on my 78 GMC to get me by for a couple weeks til I had time to fix the problem properly.
The other thing that'll nail the fuel gauge at the 3:00 position is an unplugged sender wire or damage to the wires in the sender circuit. There's only three of them and they're fairly accessible.
If the valve is unplugged you've likely found your problem.
I've commonly seen the sender wire get chowdered up where it runs along the frame rail. It's either unplugged from the harness wire that runs up to the bulkhead plug under the brake booster or something happened to it between the valve terminal B and the molded rubber round pin disconnect on the frame rail or right after the disconnect. None of that is difficult to repair.
No amount of brandy new fuel gauges will read anything without a good tank ground and good sender wires from the tanks all the way to the gauge.
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I’m doing this because none of the gages work . My fuel gage will at times will read . But 99.9 % of the time it’s at some point no specific spot on the gage it stays where it last read
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Mark
72 c20 custom camper Husky edition,
66 SS396 Chevelle 1964 Hawk, 63 Avanti,62 lark
1969 AMX ,
1968 c20 stepside ,85 K20
1977 Suburban sold
68 anniversary.
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