Article by Nestor Moya
Do your temperature and fuel gauge not work? Or do the readings fluctuate? A faulty (dirty and/or worn contact points) voltage regulator in the gauge may be the cause of erratic readings or none at all. The voltage regulator is located in the instrument cluster, specifically in the temp/fuel gauge sub-assembly, and directs power to both gauges. So if it malfunctions, it will affect both gauges at once (see Figure 3). The same source from the ignition switch provides power to the voltage regulator and the idiot lights. So if the idiot lights work but both gauges don’t, it’s a sure bet that the culprit is the voltage regulator.
Finding and repairing the Voltage Regulator
Test Operation of Both Gauges
There are three circuit board contacts on the temp/fuel gauge assembly. One is the power supply to the voltage regulator, while the other two are grounds for each gauge. (See figure 2) With a 12 volt positive lead connected to the voltage regulator and a negative lead connected alternately to the temperature and the fuel gauge grounds, each gauge should read full scale. Assemble in reverse order of removal.