1971 GTO fuel gauge and speedo..


Old 11-28-04, 10:14 PM
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Question 1971 GTO fuel gauge and speedo..

I have a 1971 Pontiac GTO. The speedometer cable is fraid and needs replaced and the fuel gauge doesn't work.. 1) how do I get to the the back of the speedometer to put my new speedo cable in (I know where it goes under the car)? 2) Is there a generic problem and troubleshooting method for old fuel gauge problems? The gauge says full even when empty. I guess if I can get to the back of the speedometer, I can check the wire connection on the fuel gauge, but if there is no problem there, where do I look next?
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Old 11-29-04, 11:24 AM
Join Date: Aug 2004
Location: USA
Posts: 539
I would suggest..

finding a book on you car. Either a Haynes or Chilton's manual. To get at the dash end of the speedo cable your going to have to remove the instrument cluster. I'm not sure exactly how you do that on your car, but this is a popular car and shouldn't be too hard to find this info.

There are three posibilities with the fuel gauge:
1. The sending unit inside the tank has gone bad or is sticking.
2. You have a Wiring problem, either no connection or a bad connection. A bad ground is also a possibility.
3. The guage in the dash has gone bad.

I would start by finding the wire that runs from the fuel guage to the sending unit, then I would use a jumper wire to jump it to ground and see if the fuel gauage moves. (It's been a while, please check me on this part, I don't remember if no connection makes the guage read full or if ground does) If it moves then it's most likely the sending unit. If no movement, then check again directly at the guage-if still nothing then it's probably the guage.

You'll probably need a lot of patience, wiring problems in cars tend to be hard to find.

Hope this helps and good luck!
Old 11-29-04, 12:01 PM
Join Date: Apr 2002
Location: Pittsburgh,Pa
Posts: 2,417
An open circuit reads full if you ground the wire it should read empty if the guage and wire are ok.A rusty sending unit ground would be where I would look first.On a car as old as yours you should be able to reach up under the dash to disconnect the speedo cable I would think,if not remove the cluster as suggested.
Old 11-29-04, 07:47 PM
Join Date: Aug 2003
Posts: 478
Get your hand behind the speedometer. If the connector is round and knurlled it un screws to remove.

If it is not a round knurled type there is an arc shaped clip made into the end of the cable housing. You push on the arc and the housing will pull out. It is easy to put it it just snaps in.

In cramped quarters it is easier if you have someone under the car rotate the new inner cable so it will fit in the square hole in the speedometer.

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