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Gas Tank sender voltage

Started by CudaHead, November 26, 2024, 12:11:52 PM

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CudaHead

Helo
      I'm working on my 1971 Challenger.
The fuel gauge is showing about 1/2 with the tank full.
It changes after it uses some fuel, going down.
This is the standard dash.
I was testing the wire at the tank.
I put a cable on the ground and another one to the wire, using a DVM.
The voltage on the wire is showing about 5.7V but it goes away fast for about 4 seconds and then come back.
It keeps pulsing signal on and off.
Do I have a bad regulator on the dash? I installed new one about 6 months ago.

DeathProofCuda

An original style dash gauge voltage limiter provides a pulsing 12-volt supply to the gauges, which averages out to about 5 volts.  The pulsing action is provided by a bimetal strip that heats up and then bends away, breaking contact through the circuit.  It then cools, bends back, and reconnects the circuit.  Sounds like this is what you still have.

I believe that the newer digital limiters provide a constant 5-volt signal.

For more information, see this Chrysler reference book on thermal-electric gauges

Your issue is more likely a bad ground connection at the tank, or a faulty sending unit in the tank.

Katfish

I'd pull the sender and check the float.
They are made of brass and prone to deteriorate and get pin holes.  This causes the float to "sink", so it never shows full.  Happened to me twice.
If you pull the float, give it a shake and it will be obvious if this is the problem.


CudaHead

I'm working on it.
I'm thinking that it's a ground problem. Still testing.