1972 Roadrunner Temp Gauge Not Working

Hi Everyone,

Have a 72 340 Roadrunner. The factory temp gauge does not move even after running for a while. Replaced the sensor, no luck.

Is there anyway to test the gauge prior without taking the dash apart?

Thanks!
Jim

If you can crawl under the dash,check to make sure the black wire from the voltage limiter going to the temp guage is plugged in.
If it is plugged in,pull it and with a multi meter with engine warmed up,and key "on" but not running see iff there is 5 volts pulsing from the black wire.
From there plug the wire back in.under the hood check for juice going to sender. should be pulsing up & down 5 volts.
Check that wire all the way to the bulkhead for any damage.
If you have juice going to both the sender and gauge but no reading replace gauge.
I am assuming the other guages (fuel,oil) are working since they share the same feed from the voltage limiter.
Hope this helps

BTW, I learned that using plumbers tape on the sender can cause an open curcuit (no ground). Engine is ground.

Thanks 68Cbarge,

Yes, all other gauges are working. I will check for the pulsing 5V tomorrow at the sender, then work my way back from there

Thanks again!!
Jim

hi

a quick easy way to test the gauge and wiring is to ground the sending unit wire then turn the ignition to on and see if gauge goes toward hot .

be ready to turn it off before it gets to 3/4 or you can damage gauge if left on !

if it moves the wire circut is good !

Pull the wire/terminal off of the top of the sender terminal & ohm the sender metal body (not the terminal at the top) to the nearby block to see if there is continuity or plug the wire/terminal back on & hold a jumper wire from the block to the body, which is the same deal & see if the gauge straightens out then I would pull the wire/connector back off of the sender & ohm the sender terminal at the top to the block with eng cold & again with it warmed up & see what ohms you get. always a good idea to pull a batt cable before switching the meter to ohms or at least confirm that what you are testing is isolated/unplugged from voltage/battery.

Hi Everyone,

Followed everyone's advice. Took me a while, but I found a broken wire in the connector itself. Replaced the connector and now at operating temperature it only comes up about 1/8 off the peg (didn't move at all before).

What should the ohms be at operating temp, does anyone know?

Thanks,
Jim