Hey everyone, got a problem. My coolant temp gauge doesn't work. I've been trying to pin-point the problem but no luck. The gages fuse isn't blown. One question is the green wire that plugs in the temp sensor in the cylinder, is i hot on Key on engine off? It should be correct? If it is, i don't have any power at the wire where it meets the sensor. Could the wire be possible broken before C100 or after? Could the gauge itself be faulty?

 

check your thermostat make sure its not sticking.

 

I had the same problem on my 79 T/A. I replaced the sensor ($5 or so) and everything started working properly. My car was running at normal temp (not overheating) and the guage was pegged out.

 

the sensor is basically a thermo variable resistor, the hotter the temp the more resistence and once it gets hot enough it will open the circuit. So I would try that replacement, also find where the wire goes to and do a continuity check between the ends for a broken or shorted wire. If those are good, start troubleshooting any components that are connectec to it and continuity check for the wires between.

 

The sensor resistance drops with increasing temperature.
So you can test your gauge like this:
- unplug the green wire from the sensor in the driver side head - with the key on, the gauge should read full left (cold)
- now ground the green wire - with the key on, the gauge should read full right (hot)
- you can optionally put a 135ohm resistor on the green wire (against ground) and the gauge should point up (cca 220 degrees)

If these tests pass, it would point to a faulty sensor.

Hope this helps.
Lou

 

Oops sorry about the temp/resistence, wasnt paying attention.must have been also thinking of the temp switch, And BBLou has it right. After I read it again I confused myself, I need to get more sleep.

 

Also your gauge could be bad, I just got back from spending some time as a generator mechanic for the Army in Iraq, our gauges went out mostly due to voltage spikes, dirt, moisture and hot*** temps. Trust me, 150* plus sucks. Anyway, a repair manual should have the ohm readings for testing. Personally I would replace it anyway if it came down to opening the console. Heck, update the dash the youd like to have.