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