Posted by Tim on April 22, 2000 at 01:29:28:
In Reply to: Temperature Gauge Needle Disapeared-due to overheating posted by Mark Davis on April 21, 2000 at 13:26:49:
Mark, if it is an electrical gauge you should also try tapping lightly on the glass. Sometimes they get pegged off the scale and get stuck, especially the older type gauges. However, I still suspect the sender unit is to blame. Here's how the electrical sender works: when ti is cold it has a weak or no ground. As it heats up it completes the ground more and more depending on the temperature of the engine. Although your motor probably suffered no damage when the freeze plug blew out, it still got pretty hot around the area where the sender was, causing it to peak inside of the sender. Newer vehicles use a Thermsistor in the sender now (Variable Resistor) which will usually withstand more due to the higher engine temperatures in todays cars and trucks.