1966 Temp guage

[Jeremy H.]

Brand new temp guage is pegged out at 250 and stays there. No matter what temp coolant is. Any ideas?
Havent tried another sending unit, but I wouldnt think that would cause it.
Thanks

Jeremy Hedges
#31711

[William C.]

Re: 1966 Temp guage

Look for a short in the wiring, pinched wire or the like. Either that or check with another gauge, "New" doesn't always mean functional.

[Kenneth B.]

Re: 1966 Temp guage

Sending unit can go bad or the wire connector can come lose.

[Stephen L.]

Re: 1966 Temp guage

Jeremy,

The temperature gauge reading goes "up" as the resistance of the sender circuitry goes "down". Therefore you probably have a short circuit in the sender circuitry such as a pinched wire which would cause the resistance to be near zero and the indicator pegged.

If you want to test the indicator while in the car disconnect the sender and replace it with a resistor of about 100 ohms. Tie the end of the resistor to the wire and the other end to a good ground.
If the circuit is good, you will read about 180 deg +/- on the meter.

I did a test on my meter using a decade resistor box (in place of the above resistor) and got the following results:

Decade Box Temp indicator reading
52 ohms 250 deg
55 ohms 245 deg
60 ohms 230 deg
80 ohms 210 deg
85 ohms 205 deg
90 ohms 200 deg
95 ohms 190 deg
100 ohms 180 deg I assume the "tick mark" between 100 deg and 210 degrees is about 180 deg

The indicator scale face is non-linear so my readings are interpolated for those that are between the actual indicated values.

Hope this helps