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Seen several posts regarding fuel gauges...here's my problem, sometimes mine works and sometimes it doesn't. Ran out of gas the other day, put five gallons in and the gauge went up. Next day...no reading. Tried to ground the lead coming off of the sending unit (aligator clip inside plastic cap on end of wire attached to wire, attached to frame), and the gauge did nothing. Today my gauge seems to be working???

Any ideas on how I can further trouble shoot this problem?

Thanks in advance!
 

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Trace the wiring back. Spray WD-4 in every connector and plug and un-plug them several times. You may be also to SLIGHTLY squeeze the female sockets with a pair of long nose pliers. 10 ohms to ground should cause the gage to read maxiimum scale.
 

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The sending unit in the tank supplies the ground for the gauge. Disconnect the wire from the sender and ground the wire. The gauge should then read full. If it doesn't, the gauge or the wiring is bad. If the gauge goes to full like it should, then the sender is probably bad.

Dave J

My wife says if I buy another Mustang, she's gonna divorce me. I'm sure gonna miss her....
 

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Like the others have said, troubleshoot to figure out the source of the problem... Someone mentioned it before, but I will again anyhow, ground out the wire back at the sending unit, this should peg the gauge to full. If it does, the sender is the problem, you can either repair or replace it; I replaced mine. HOWEVER, if this doesn't peg the gauge, there are a few concievablepossibilities: the wire going between the sender could have a short in it, pull the gauge panel (you're gonna have to do this anyhow w/ the other possibilities) and test for conitinuity between the - post on the gauge and the wire back at the sender. If you have conitinuity, then there is something wrong on the + side. At the + post of the gauge, depending on the quality of your multimeter, you should see approximately 5 volts; if you have a good meter (I have a few, my best meter is a Fluke, and it does this, my cheaper ones don't), it will not read steady because the voltage regulator is opening and closing. If you read ~5V at the gauge, the gauge is bad. If not, the VR is bad, or there is a bad spot in the circuit betweent the VR and the gauge or the VR and the +... Good luck!

-Jason

'72 Mach 1 || '90 Talon TSi AWD
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"Thats not a leak, my car's marking its territory!"
"If you've done it, it ain't braggin'." -Roy Rogers
 

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sending unit is a variable wirewound resistor with pickup tang that runs along resistor dependent on fuel level. wire wound resistor or pickup tang connection probably problem after you check previous posters wiring checkout. the assembly is a well made unit and if your float (a part of the sending unit assembly is good - no fluid sloshing when shaken) you can rebuild unit easily. to rebuild take cover off sending unit "box" and clean variable resistor and pickup tang with very fine emory cloth or sandpaper, to check operation attach ohmeter leads from case to output wire and move float from top to bottom and note about 10 ohms at one end and 80 ohm at other end. also slowly move arm and note any discontinuities or dead spots. Or you could spend about $20 and get a new unit - you have to drain tank in either case.
 
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