Gauge Reads cold, heater works.

[atoyot]

I've had this '91 pickup 4 cyl 22re for a couple months. It always reads right on the cold line. It moved up about a 1/4 driving through redding in 105 degree temps.

I was thinking maybe the thermostat is stuck open? But the heater works. Could it still be the thermostat?

It always starts fine in all temps. And runs fairly smooth. Sometimes it runs slightly rougher when its real hot.

 

[KLF]

I would suspect the 21 year old stock inaccurate factory gauge first.

 

[atoyot]

I suppose I could pick up an external gauge to see if it matches the stock gauge.
I'm suspecting one of the sensors but if it's the gauge I can live with that.

 

[KLF]

There's a very detailed troubleshooting procedure in the FSM. The sender is the little single-terminal one down on the lower intake manifold, between cyl #2 and 3.

 

[Bogo]

Also 21 years of terminal corrosion can mess with sensor readings... Considering it is a NTC type sensor, higher resistance looks like it is cooler so a corroded connector would read cool at the gauge.