Engine/Transmission (1994 - 1998) Temperature gauge reading less than it has

[scotty-u]

Over the past 6 weeks or so I have noticed that my temp gauge is not reading as hot as it normally does, nor does it rise and fall with the opening and closing of the t-stat. It still throws the heat out of the heater and defroster vents. Antifreeze level is full, water pump not leaking, belt is running correctly. With the recent cold snap here in PA, I added a piece of cardboard just behind the grill, and a recent hard pull up hill with the loaded dump trailer didn't raised the needle from where it has been running. Have not taken the time to clean the wiring connections at the sending unit. Do the sending units fail like this? Do I need to put a second gauge on to check the factory one?

 

[hsmith]

Probably a piece of the rubber seal is hanging the tstat open.

 

[Matt42]

Probably a piece of the rubber seal is hanging the tstat open.

That's likely true. If the diagram in the factory TSM is followed for installation, it puts the rubber seal in backward. That will sort of work OK, but it will often make the engine run cold (or warmer), and can cause part of the rubber seal to hang up in the thermostat. Do not ask how I know this.