Temp Sensor Mystery

[TsherryUSA]

So my temp gauge / sensor on the dash has never really worked. 99% of the time it reads cold on the bottom. Doesn't budge ever. It will go up to the middle if I'm blasting heat and driving up a steep hill, but not always(?).

I've tested the gauge by grounding the plug. Gauge works in that regard.

I recently replaced the thermostat and took the opportunity to change out the temp sender unit. Used this part: TU241 https://www.autozone.com/engine-man...ture-switch-tu241/195656_0_0?searchText=TU241

Only thing I can think of is that this isn't the right sending unit. Any suggestions for troubleshooting this?

 

[tinman_72]

Strange that blasting the heat makes the gauge go up. If anything, running the heat will make the gauge go down a little as you are drawing heat from the cooling system and transferring it to the cabin.

 

[TsherryUSA]

Strange that blasting the heat makes the gauge go up. If anything, running the heat will make the gauge go down a little as you are drawing heat from the cooling system and transferring it to the cabin.

Well it was probably a bit unique. Driving up a steep hill to Timberline Lodge ski resort at midnight in winter...
I guess I haven't tested it with AC since replacing the sensor because... winter

 

[C420sailor]

Turning on the defroster commands AC compressor engagement, regardless of temp setting

 

[joney]

So my temp gauge / sensor on the dash has never really worked. 99% of the time it reads cold on the bottom. Doesn't budge ever. It will go up to the middle if I'm blasting heat and driving up a steep hill, but not always(?).

I've tested the gauge by grounding the plug. Gauge works in that regard.

I recently replaced the thermostat and took the opportunity to change out the temp sender unit. Used this part: TU241 https://www.autozone.com/engine-man...ture-switch-tu241/195656_0_0?searchText=TU241

Only thing I can think of is that this isn't the right sending unit. Any suggestions for troubleshooting this?

Previous discussion possibly relevant? water gauge temp sender