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After replacing the fuel sender, my fuel guage was finally working, took it in to the mechanics to get the AC worked on (which runs great now) and the fuel guage quit again. Whats going on?

Proud Owner of a 1969 Mach 1<P ID="edit"><FONT SIZE=-1>Edited by herponi on 04/18/01 05:41 PM (server time).</FONT></P>
 

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They could've bumped one of the gauges, or there could be an electrical short somewhere.

My growing conclusion is that mechanics DO NOT KNOW HOW TO WORK ON CLASSIC CARS. Every time I take my Mustang in to my mechanic that works on my girlfriend's '96 Mustang, my baby always comes back needing more work. They always screw something else up, in fixing what I need fixed. Bah. They never mess up my girlfriend's car.
 

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Do the rest of the gauges work right? If so, we'll assume the CVR is working and that the cluster is grounded propperly.

Check that the wire is still attached to the sender at the tank. Test the gauge and wiring by disconnecting the wire from the sender and ground it. Turn the key to "on" or "accessories" and see if the gauge pegs (only do this long enough to see the gauge peg or it will damage the gauge). If the gauge pegs, the problem is in the sending unit. If not, the problem is with the gauge or the wiring between the gauge and sending unit.

If you always do what you've always done,
You'll always get what you've always got

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If you put in a re-pop unit, there might be the problem. I went through three until I came off the money for a good one.
Next, check the push on connection at the gas tank. (might have fallen off or loose)
Next, check to see the tank is grounded. You should measure zero ohms from the base of the gas sending unit to the chassis. The sending unit is nothing more than a variable resistor in series with the fuel gauge.
Last, drain the tank, remove unit, check with an ohm meter. You should get about 3 ohms (full, and 40 ohms (empty)
good luck

32stangs
 

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One thing that can cause guages to work intermittently is bad grounding of your instrument cluster. Check that out before you replace the sender again.

Glenn Morgan: 66 GT V-Burgundy Fastback 351w+toploader+9 in. TracLoc. Started out as a rusted-out Chicago-area crusher. After sacrificing a solid 66 coupe for its sheetmetal sub-assemblies, I have one solid (and expensive) work in progress!
 

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I had the same problem....

I just cleaned off the connector on the sender, and cleaned the corrosion off of the wire connector with a small round wire brush.

Worked great after that..

http://my67heven.tripod.com/emsm.gifI was looking for a restoration of fantasy. I do not want my car to be as it was in 1967. I want it to be as I imagined it in 1967. -John Baird
Got Rust? 1967 A-Code Coupe
 
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