Why doesn't my 64 Tbrid temp gauge work?


Asked by Dec 11, 2017 at 04:34 PM about the 1964 Ford Thunderbird

Question type: Maintenance & Repair

I have 5 volts at wire to the temperature sending unit (only a single wire to
it).  The temp gauge goes to max when i ground that wire.   When the car is
cold the resistance of the sending unit was about 2000 ohms to ground;
when the car was warmed up, I measured the resistance of the sending unit
to ground to be about 160 ohms, but still the temp gauge was still at
minimum.   When I put a 28 ohm resistor between the 5v wire and ground,
my temp gauge reads about 1/4 scale.   Everything seems as it should, the
only thing I can guess is my gauge may be faulty...

8 Answers


I'd replace the sending unit , don't use Teflon pipe sealant or tape on the pipe thread a little grease will be fine The gage sound to me is as it should

2 people found this helpful.

Since the gauge swings to hot when grounded the gauge and the wiring are good. As olds403 said don't use any sealant on the threads of the sending unit. Another possibility is your thermostat is stuck open and not allowing the engine to reach operating temperature (195°F). How's your heater working? If it's not or only luke warm I'd suspect the thermostat. HTH. -Jim

1 people found this helpful.

Thanks guys, I will change both the tstat and the sending unit (they are cheap enough) I'll order from Macs and post my results. Thanks again..

1 people found this helpful.

You're welcome. Glad to help. Keep us posted. -Jim


Well, I changed the sensor (no tape, and I checked for continuity between sensor base and battery) and still the gauge does not move?! The cold resistance was 640 ohms, hot it was 64 ohms, and motor was too hot to keep my paws on, so tstat must be good. The 5v wire and clip are good too. I'm thinking its got to be something with guage...unless I'm missing something..

1 people found this helpful.

Ford products of this era had a voltage regulator behind the instrument cluster and attached to the back of the cluster. I'm wondering if that's your problem? This is actually a very simple circuit. Gauge is hot with the ignition on and the sending unit is a variable resistor to ground. Or possibly a corroded or dirty connection at the gauge terminals themselves. But since the gauge swings to hot when the wire at the sending unit is grounded that should eliminate everything except the sending unit, which is new and appears to be working. Hmmmm. HTH. -Jim

1 people found this helpful.

Thanks Js08016. I have the updated "chip" type regulator, not the old wirewound type. It puts out a steady 5vdc. The oil pressure guage and fuel gauge both run off same regulator and both work. I'm thinking its got to be corroded or like, terminals/wiring to/at the temp gauge like you say. Or the gauge is damaged/out of calibration. Anyway, that's my next step to get behind dash and check wiring and connections and guage..when the weather allows....pretty darn cold now lol...

1 people found this helpful.

You're welcome. Glad to help. Keep us posted. I'll be curious to see what you find out. -Jim

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