temp guage pegged out !

[kl92flair]

I have a 93 corolla that as soon as the ignition is turned on the coolant temp guage goes all the way to the top. This car is NOT running hot, I've replaced the sending unit (single wire) and the coolant temp sensor. Both of the cooling fans work as they should and when they should. I'm thinking I've got a dead ground somewhere I just dont know where to start. Some times after the car is warmed up it will suddenly drop to the normal position on the guage and usually stay until you cut the engine off, then it will peg out again when the engine is restarted. Any suggestions ?

[Bitter]

could be a bad gauge.

[kl92flair]

I'm pretty sure if you test a gauge you you ground it out to see if it will peg, if it does you know the gauge is ok. By the way it works sometimes I'm thinking somewhere the lead from the sending unit is grounded and was wondering if this is a common thing with these cars. Just hoping someone else had this type of trouble and could offer some advice about where to start looking.

[blb]

The wire to the sending unit is shorted to ground at some point.

[kl92flair]

Thanks for confirming my suspicion about the cause of this. Here is another strange clue, when its hot outside like it is here in Ga. today- 97" the gauge worked. It started at the cold position, went to the normal operating position and stayed there all the way home, 25 miles. Anyways these wiring things seem to be more complex than they usually are. I've got a good multimeter, I'm sure I will find it eventually !

[Steelballz]

if it is the wire grounded, as far as i can remember its a yellow that goes into the interior loom connector (long 22-pin), as a pointer

might be grounded in the bulkhead grommet, on the engine somewhere, or behind the dashboard which will be very annoying to trace...