I have a 2006 f-150 5.4, and my temperature gauge flat lined and my A/C no longer blows cold. I also got a CEL. When I pulled the code it was a P1289. I did some research and thought that the CHT sensor went bad. I took it to a Bring Your Own Parts (terrible experience, wouldn't recommend to have it replaced by I don't have the mechanical ability to do it. They replaced the sensor but to no avail.

I'm pretty certain the two are connected because for a short period of time when I would accelerate the temp gauge would work and the ac would blow cold.
Any thoughts?

 

Does the compressor still cycle?

 

What do you mean when you say your temp gauge flat lined? It's reading all the way cold? All the way hot?

The temp gauge on your dash has no affiliation with your ECT or CHT sensors. The gauge has its own temp sender.

A faulty fan clutch could be the culprit. At low speed, or idle, your fan may not be drawing enough air across your radiator, thus raising coolant temp and also not cooling the condenser behind the radiator. Increasing speed increases airflow across both, thus cooling the engine and refrigerant.

 

The compressor is not cycling at all.

The gauge reads all the way cold and the coolant temperature stays the same. It's not an issue of the engine cooling more of the gauge doesn't work and the AC doesn't blow cold ever

 

I believe there is a harness that the CHT and A/C compressor share. Can you try and remove a few things to get a look at the harness under the intake manifold? It seems most likely an electrical system failure as neither system share any hardware.

 

Well everything is solved. Took it to the guy who rebuilt my engine a few years ago to get his input and when he wasn't sure referred me to an electric shop up the road. He replaced the harness like you said and everything works better than ever

Thanks for your help

 

What harness did you replace mine is doing the exact same thing

 

how much was the harness my is doing the exact same thing

 

what harness??