Temperature gauge reading low

[Pampas56]

1989 K2500 ECLB

My temp gauge is reading low and erratically.

This is the best it does. I'm thinking it should be closer to 210F not 150F.

This is what it has been doing lately. Sometimes it WILL get to 150F, but i can't really depend on the reading.

I don't think the truck isn't getting up to temp because the heater works and it seems to be running closed loop. Thermostat is 195F and has been changed a number of times. The gauge functions as it should- maxes out on startup and comes up as the rig heats up. Just not as far as it should.

I suspect the sender is the problem. The ONE wire one in the head.
Attachment 2410180
I have looked at the Delphi spec sheet. Are there different resistance curves or just one?

I also discovered that my sender is a button type and the replacements are all spade type. Thought I was going to hafta get a different connector. Found out this connector fits both!



Any help or advice would be appreciated
Steve

[gmc 2500 4x4]

Definitely replace it with what you have, isn't there one by the thermostat housing?

[Accelo]

Inaccurate gauge readings are a prevalent complaint after changing out the factory sensor.
Aftermarket sensors are a shot in the dark.
I have a report somewhere that lists the resistance of the various aftermarket sensors. They were all over the map, and most were not even close to the GM specifications. I recommend a GM/AC Delco sensor and no thread tape to install it.
Usually will fix the issue.

[Pampas56]

Originally Posted by gmc 2500 4x4

Definitely replace it with what you have, isn't there one by the thermostat housing?

That is the two wire SENSOR for the ECM. I am working on the one wire SENDER for the gauge, on the head between 1 and 3 spark plug.

[Pampas56]

Originally Posted by Accelo

Inaccurate gauge readings are a prevalent complaint after changing out the factory sensor.
Aftermarket sensors are a shot in the dark.
I have a report somewhere that lists the resistance of the various aftermarket sensors. They were all over the map, and most were not even close to the GM specifications. I recommend a GM/AC Delco sensor and no thread tape to install it.
Usually will fix the issue.

I seem to remember reading something about that. If you can find the report, I would like a copy. Maybe save it as a Sticky if the Mods are agreeable.