Expert: Skip Bollinger - 3/18/2009

Question
I have a 1998 Toyota Tercel. When I turn on the ignition the needle on the temperature gauge immediately goes past the maximum and will not go down. It falls back below zero when the ignition is off. what could be the problem

Answer
Everett,
  I'm a Parts Professional, NOT a Tech. I am not qualified to answer this question but will offer two (2) thoughts for you to consider.. Please remember, in my Profile, I state that I'm a Parts Professional, NOT a Tech.
  The first things that come to mind are a bad Temperature Sending Unit or wire.
  Start the car and let it warm up. With the key in the "run" position, (the engine does NOT have to be running now) remove the wire from the sending unit. What does the gauge read? Note that gauge reading and just "strike" the wire to ground, momentarily, like the intake manifold. What does the gauge read? Are there any differences in the two readings? If there are differences, I'd proceed to the next paragraph.. IF not, the wire is grounded someplace between the gauge on the dash and the sending unit.   
  I would remove the Temperature Sending Unit from the car and take it to your local parts store and ask to see a new one. I would also take an Ohm meter. I'd compare the Ohm's resistance from the old one to the new one before purchasing it. If the Ohm's are the same, I wouldn't buy it and look for someone smarter than I am for help.
  That is the best I can offer. Please remember before you slam me for being stupid, as stated in my Profile, I'm a Parts Professional, NOT a Tech.
  Good luck and I hope this may help a bit.
Skip