Join Date: Mar 2002
Location: Austin, TX, USA
Get a variable resistor of about 1K to 5K ohms. Attach the wiper (center terminal) to the sender wire. Attach one of the other two terminals to a good ground. Turning the pot should sweep the guage. I think operating resistance is in the neighborhood of 100 ohms but I'm not certain of that. In any case, you should be able to diagnose the guage.
Take a resistance reading off the sender between it's unconnected terminal and the block. When hot it should be in the 100 ohms range and cold it should be several hundred ohms to thousands. It may be the other way around, but at least you'll know if it is changing resistance with temperature.
68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI