Read a couple threads trying to find some other tests to run but basically my needle was working fine then noticed it not climbing past like 1/4 of the way. For a while with AC on i would see it jump up past 1/4 but then that stopped. So now it doesnt ever move past 1/4 way. I hear when my thermostat opens and when the Rad fan kicks on but needle doesnt move. I replaced the sending unit with a new one, the old one surprisingly tested OK heating and cooling, resistance changed within ranges. Tested the wire to the unit grounded out and my wife saw the needle jump really fast all the way up, she said it took a second and then the needle jumped. I thought it would climb gradually but she said quick jump.

On startup the needle will obviously move from its limp OFF position to that 1/4 way point but no matter what it wont move any higher. Being that I have some cluster dimming issues too im wondering if the cluster itself has an issue or an input wire is going bad.

 

bump any suggestion? take apart cluster?

 

 

BUMP. So took out cluster again to look for loose screws and bad solders. Tightened all the screws on the back of cluster...now needle pegs to H as soon as I turn the key on. It will do it both key ON and starting car. Needle doesnt come down just stays there. Still sound like bad gauge? Bad ground somewhere? T-stat ground is clean and good. Idk where the cluster ground is off hand.

 

Unplug the temperature sender, which is screwed into the engine head underneath the distributor and has one wire. Gauge should stay at cold then. If it does not, there is a short in the sender wire to ground, or a bad gauge.

Engine temperature low and varying during driving is usually because the thermostat is stuck open.

 

Yeah I know its not a T stat issue because as soon as I turn the key the needle climbs. Is there a way to test the gauge itself? I grounded out the sender wire previously and the needle moved to H so I assumed the gauge was ok. Guess I'll hunt for shorts in the wires.