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Classic/Antique Car Repair/1967 GTX GAS GUAGE NOT WORKING

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Expert: - 2/28/2011


Question
I have checked and confirmed that the sending unit in the tank is good. I do not know if the problem is the guage or the circuit board.  How can I test them?  Can the board be repaired or does it have to be replaced?  Thanks in advance for your advice.

Answer
First, if you are handy with a soldering iron, most circuit board problems can be repaired. Now, a digital voltmeter can be used to check the under dash circuits. There should be voltage at both sides of the fuel gauge behind the dash. Ford uses a constant voltage control behind the dash between the ignition switch feed and the gauge unit. This stops voltage fluctuations from causing false readings. The voltage into this unit is battery voltage and somewhere around 6 or 7 volts out. That is the voltage that you should see at the input side of the fuel gauge. To test the gauge operation I use a small jumper wire across the out terminal of the fuel gauge once the tank wire is disconnected. With the jumper connected to ground the gauge should go to full and to empty when disconnected.  

Classic/Antique Car Repair

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Brad Sears

Expertise

All automotive including antique and collectible. However if the car has been modified I can only answer in general terms and maybe get you pointed in the right direction.

Experience

Automotive tech instructor. Syndicated auto columnist 1970's though the early 1990's. Syndicated auto radio talk show, Ask Brad About cars, CBS Radio 70's through 90's TV Show "Last Chance Garage" 1980's PBS-TV syndicated. Auto instructor for the following companies: Fram Autolyte Holly Carter AMF Ford Motor University Of Conn Blue Hills Technical School Sugar River Technical Center Grew up in a family garage in Needham Mass and turned wrenches from the age of 14.

Publications
Manchester Union Leader, Nashua Telegraph, Motor Service Magazine, Yankee Magazine, Popular Mechanics (Saturday Mechanic early 80's), Los Angeles Times, New York Times, and lots more.

Education/Credentials
More than I care to remember. Basically Franklin Technical Institute in Boston, Northeastern University, Fitchburg State Teachers College, Tufts University, and a lot of factory schools along the way.

Awards and Honors
Moto Award winner. And much more.

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