Questioni read the answer about the 65 gauges and thought I had mine fixed. I have a 67 mustang. There are new sending units in the fuel tank and for the temperature. There is also a new instrument voltage regulator. The gas and temp gauge worked for a day, although the readings kept fluctuating. Then they quit entirely again. The hot and ground are still hooked up. What else could it be?
AnswerSince both gauges are acting up at the same time, the problem has to be caused by a bad instrument voltage regulator, or else a bad connection to it or to the gauge cluster itself - maybe a bad ground connection.
To check the instrument voltage regulator, use a test light or a voltmeter to see if there is a pulsating voltage on the terminal that goes to both gauges. With the key on, the meter should jump from zero to 12 volts, about once a second or so, or else if you use a test light, it should blink about once per second. If you see that, the regulator is working right. If you don't, check the power connection to the regulator again, and the grounding of the voltage regulator - one of those things must be not making good contact, or else the regulator has failed.
I can't see any other explanation.
Dick
