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69 fuel gauge

6

69mstng

Member
My fuel gauge is not working. It quit last spring. The sending unit is fine and the VR in the dash is working. I had the dash apart last night and just got confused with all the wiring. lol Any ideas what the problem could be?
 
Take the line off of the sending unit and briefly ground it with the key in ACC. Does the gauge peg high? If so, then the problem is in the sending unit or its ground. If not, leave disconnected and disconnect the plug near the driver's side kick panel and measure continuity between there and the sending unit line (yellow/white wire). Should see 0-1 ohms. If kilo- or Mega-ohms, then the line is broken somewhere between the two. You can do the same between the harness plug and the dash plug insert. Do these other tests with the battery disconnected to be safe.
 
I tried to ground the line to the sending unit and got nothing. I mesured the continuity of the (yellow/white wire) between the harness plug and the dash plug and that was ok. I dont think i am getting power to the gauge its self. There should be a power wire to the gauge and the other wire to the sending unit correct? If so what color is this power wire?
 
The power for the gauge is supplied by the CVR that snaps onto the circuit board. If it were bad, you'd have no power to any gauge. The power travels along a trace on the circuit board from the CVR to one post of the the gauge. The other post goes to a trace that goes to the sender wire.
 
My other gauges (temp and oil pressure) are not hooked up. I have after market gauges for those in the car. My dash lights work. I put a new CVR on yesterday because i thought it was bad. But that didnt fix my problem.
 
I took a hot wire and put it on one of the post on the fuel gauge to see what it would do and the gauge shot way past the full mark. I know my tank is not full. Could the printed circut board be bad??
 
Yes, your circuit board could be bad. You could just jumper a wire from the CVR to the + side of the gauge, since that's the only one you're using. Putting a full 12v to it would definitely peg the gauge.

At least you now know that it's not the gauge!
 
I ran a jumper wire from the CVR to the fuel gauge and it just pegged out the fuel gauge. I put my test light on the CVR there is power going in at one end but no power going out the other end. shouldnt there be power coming out the other end of the CVR? This is a new CVR. Should a new printed circut board fix all this? Or do i have other problems?
 
"69mstng" said:
I ran a jumper wire from the CVR to the fuel gauge and it just pegged out the fuel gauge. I put my test light on the CVR there is power going in at one end but no power going out the other end. shouldnt there be power coming out the other end of the CVR? This is a new CVR. Should a new printed circut board fix all this? Or do i have other problems?
Click to expand...

The output of the CVR is very difficult to read on a DVM or test light. It may not show up on a test light, but a volt meter will show a very jumpy DC reading. If no reading whatsoever, that indicates a bad CVR.
 
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