2008 1500 SLT 5.7L 4WD

Past week the truck has been overcooling. Thought thermostat was stuck open so replaced it on Saturday. Same issue. Replaced the temp sensor today even though my scanner was giving correct readout of the temp. Still overcooling/not getting to full temp, or taking A LOT longer than normal to reach full temp.

I did notice that the AC fan is running constantly with the selector in defrost. Switch to vent and it will shut off. Turn blower fan/system to off and fan will stop. Problem is I always keep the selector in the defrost/foot position.

This whole time the temp selector is in the hot position. AC button is off.

With this said, I was thinking the TIPM connections could be corroded causing the fan to constantly run. With it running, I'm thinking it's pulling cold air in across the motor and cooling the motor itself. I cleaned them with contact cleaner and put some dielectric grease on. Issue continues.

I'm thinking the TIPM is bad somewhere or something is going on with it.

Anything I may be missing? I unplugged the AC fan for now. Haven't ran truck yet to see if it helps.

 

UPDATE:

Well, AC fan is not the problem. 50* this morning and still didn't get to operating temp.

 

What brand thermostat did you install? Sounds like it really isn't doing the job it is supposed to....

 

Just threw a Duralast in.

Everything was working normal, then it started to not get to temp. Thought thermostat was stuck open. Changed. Same issue. Thought maybe sensor was not reading correct. It was according to my scanner. Changed it anyway. Same issue. Noticed AC fan constantly running. Thought maybe pulling air across motor, cooling it. Unplugged fan. Still same issue.

No leaks. System build pressure. Not losing coolant. Heat still blows hot. MPG's down due to not operating at full temp.

 

Get a Stant super stat, but, NOT one of the 'failsafe' fellers. I just don't trust the duralast parts.....

 

Not one local at all.

 

Check that the temp sensor plug has a good ground. The ground is the "taller T" of the two.

 

Just double checked the fan clutch and there is some slop in it. Even though it spins fine by hand, maybe it's enough drag to cool it???? Going to get a new clutch and put on now.

 

FYI your electric A/C fan will run when you have the defrost on because modern vehicles have been set up to use the A/C compressor to help pull moisture out of the air blowing on your windshield.

 

So, it IS supposed to run constantly as long as the mode selector is in the defrost position? Even with the temp selector on hot and AC button off?