my temp gauge when the car is both on and off is reading off the high end of the gauge, like 300 degrees.

I took the gauge covers off and tried to turn the needle back to 100, and as soon as i turned the key on, it went right back to over 300...

is the gauge bad??, is the sending unit bad??, or can i simply take the needle off and re-clock it back to where it needs to be.

also, on my 88 305 TPI car, where is the sending unit located at if I need to change it??

I just bought the car, got it running good, and it overheated on me on the first trip. the water pump was leaking out the weep hole, so i replaced it as well as installed a 180 stat. I am a little nervous to drive this thing now in rush hour traffic and not knowing whether its running hot or not.

also..should my fans come on as soon as i turn the key on??

 

Temp sender for the gauge is in the drive side cylinder head, spade connector, between the #1 and #3 holes. Replace that before you go messing with the gauge.

 

James, mine does the same thing, it will peg at the top when you turn the key to start. I pop the dash pad just bove and it will come back down. The sending unit for the temp gauge is right next to the thermostat on the intake. The fan switch is on the bottom of the right head between #4 and #6 cylinder. The fan should not come on until the temp gets up to about 230.

 

Just unplug the wire on the sender. Disconnecting it is inifinite resistance, which would make a working gauge go down to the lowest temp setting. If it doesn't go back its not the sender.

 

I just resolved a similar problem with my fuel gauge.
The fact that bigbike1500 needs to hit his dashpad confirms that oxidation forms where each gauge connects to the hidden circuit board behind. I had to pull out the dashpod, pull the gauges, pull the clips to the circuit board, and reassemble, after a very light cleaning with a pencil eraser.

But by all means, replace or do a basic test on the sender 1st.

Seth

 

I replaced both sending units, and freed the stuck needle from the metal cup that the gauge sits in.

it works now, but I have a strong suspicion that its not accurate.