Intermittent Warm Air From AC

[Racer25]

Can’t figure out AC problem with 2005 Dodge Ram 2500 Diesel.

Three times now, the AC works for maybe 4-5 weeks then starts blowing warm air. Freon level good. Shop can’t figure out or find any issue. I’ve taken to them twice where they evacuate freon to check amount, and call to say it’s working & don’t see a problem. Was cooling recently but started blowing warm air again. Last several days was cool outside so I turned thermostat all the way to warm & ran this way for 2 days with AC off. Yesterday, turned thermostat back to cool, turned AC on, and it’s working again? Any clues? Maybe a defective warm/cool panel button (assume that might be a thermostat)?

 

[jws123]

Next time it happens pop the cood and see if the compressor clutch is engaged and running if it is then you have a blend door getting stuck.

 

[bgenlvtex]

I fought the dealer tooth and nail over this stuff on a 2006 3500 drw. It went on for months and ultimately only came to a head because I had a loaner vehicle that they wanted to sell. It is a long story, but here is the short of it.

They replaced most of the system, some of it twice, told ridiculous lies, billed the extended warranty company (and me for rubber parts) many thousands of dollars for their profound incompetence, but refused to change the controller because it "scanned good", and in the end said "We can't fix your truck".

I told them to write me a check for the extended warranty that is no good (because they can't fix my truck) and the parts/labor I had paid for already OR replace the controller. Under duress they replaced the ($60 some odd dollar part) and the problem was cured.

"defrost" is the default failure mode for the controller (for safety reasons I'm sure), when it is failing intermittently it will switch to defrost which brings hot air from the heater core.

If you know the blend door is not broken and is functioning as it should, but you are getting intermittent "heat" while the a/c is on, I would replace the controller.