General Motors temperature gauge troubleshooting
Temperature gauge troubleshooting begins with isolating the problem either to the gauge, sending unit, fuse or wiring. As with any electrical troubleshooting it is best to check all wiring connections are clean, tight and free of corrosion.
The following process must be preformed with the ignition key turned to the “on” position. The first place to start is at the temperature-sending unit. Remove the wire from the temperature-sending unit located on the engine (typically a dark green wire). Then connect the wire to a good ground. You can do this by using a jumper wire. Check the gauge, if the needle points to “Hot”, replace the sending unit. If the needle does not move, remove the same dark green wire from back of the gauge and connect a jumper from the terminal on the back of the gauge to a good ground. Check the gauge if the needle moves toward “Hot”, the wire from the gauge to the sending unit has an open or bad connection. If it does not move, connect a test light by grounding one end to a good known ground and the other end to positive side of the gauge (typically a pink wire). If it does not illuminate, ensure the gas gauge fuse is good. If the fuse is good, connect a jumper wire between the ignition switch and the positive side of the gauge. If the gauge now works, replace the defective wiring between the gauge and the ignition switch. If the test light illuminates there is 12 volts present, replace the temperature gauge.