guage pins out over 260 when car warms up and then jumps down to 200. i replaced the thermostat and antifreeze and still the same problem. dont want to keep dumping in money if it is not the problem. has anybody had the same problem if so what did you do to fix it? also it is on my 87

 

Mine is doing the same thing but I believe that you, like me, are going to need to change out the sending unit screwed in the passeger side head. Mine is original to the car which is 1982!! Guess it's time for a change.

 

hopefully thats all. i was just going to change the one in the thermostat housing next but ill try the other then. thanks

 

That one is for the computer info to the ECM. The one in the head is for the gauge itself.

 

i thought the one on the head was for the ecm because that was the one i replaced for the fan switch which runs by the ecm.

 

I'm not sure about that since my car has a mechanical fan and no ECM, but I do know that the one on the head if disconnected kills my temp gauge, no reading. Now maybe on yours the wiring ties into something else such as your fan, that I'm not sure of. I would think the one on the thermostat housing could be part of the ECM for the fan and such but maybe not. Is there another one in the other head?

 

the one in the intake manifold is your Coolant Temp Sensor for the ECM

the one in the head is your Sending Unit for the gauge

mines all jacked up too... i replaced the CTS, and decided if that didn't fix it, then I don't care, because at least the COMPUTER knows how hot it is and when to turn the fan on.

and it does, although my temp gauge will be all over sometimes, the fan always seems to turn on at the same temp under the same conditions.