So todays update. Ac was filled back up and was working like a charm, with normal pressures. I took my dog to the park and when I got back into the LR no AC. I am at a loss. I have read the shop manual over and over several times trying to understand this electrical system and how it controls the AC. Complex is an understatement. I am going to replace the evaporator temp sensor to rule out that next. Anyone have ever replaced this before and have suggestions or tips?

 

Update: I purchased the IID Tool and preformed some updates on the BCM and cleared codes. After this I was able to get the AC to work again, however it wasn't long before it shut off again. The code I am getting when the AC fails is U0424-68. Invalid Data from HVAC control module. Not sure what would cause this or if anyone else has ever received this message.

 

When I clear the code the ac works shortly after. Thoughts?

 

Sounds like the control is going bad and when you reset the codes it works until the computer throws another code and shuts it down.

 

Weird.. but very good clue as 99.99% of HVAC problems are focused under the hood or with leaks, AC compressor, etc. IF its actually the HVAC control module then I'd definitely look into that first before you spend a crazy amount of $$ chasing down something that isn't there.

Unfortunately since it's totally solid-state and a PCB there isn't much you can do to test it.

I would look at what data the HVAC module actually supplies to the other components and the computer which stores / reads the codes. It's possible and likely that there are other pressure sensors on the evaporator and other parts which may feed data to the computer. Probably many temperature sensors as well including cabin air temperature. Can you play around with the heat in auto mode and see if everything works as advertised? If it's unable to maintain correct temperature regardless then that's an obvious sign it may be one of the cabin air temp sensors.

Set it to like nearly ambient and make sure it doesn't turn on full hot (should be equal temp) then set it to max / high temp and verify it's bumped up to very hot air. Both times in auto mode of course. I suppose you could even set both temp dials to full cold in ECON mode and verify it's pulling the coldest ambient air it can.

That would rule out many of the cabin air temp sensors, ambient air temp sensors, and the blend flap servo motors inside the hvac air box without even using the AC system.

 

Hello,

Did you find a solution to your problem?
I have the same code U0424-68 and my driver seat a driver windows' switch panel doeas not work at all.

Thnaks.

Martin