I'm so glad I found this site. We have a 2007 Aspen with 140 000 km. We live in Canada and our heater about once a week will just not throw heat. The fan works but we can't change it to defrost or feet vents. It only blows cold air.
I've had it at the dealership several times with the following explanation "we diagnosed it electronically ($45.00) and have reset it ($35.00)"

Usually when you turn thr key off and then restart a few times the heater will work fine again until the following week. We always have a blanket and ice scraper just in case we get caught on one of our cold trips.
Anyone else have any problems or offer any solutions?
Cold in Canada

 

If you can get it to work by cycling the key, and the dealer can get it to work by ECU reset,...

I would be willing to bet the HVAC controller is Toast..BUT....

Before replacing it, go to a different dealer, and see if a software update is available.

 

I've had this problem almost since I bought my Aspen hemi limited at 114k. I tried fuses, key turns, battery resets..ONE THING almost always (95% of the time) works...
start at HIGH in climate control, press both zones at same time to go to LOW. Once you hear it engage the cold side, press both zones at same time but this way go back up to HIGH. The system will then engage heat, and you should be nice and toasty. I swear this works. 221k on my hemi limited. Heat is cranking with the climate control problem, and vice versa to engage ac/cold side. Hope this finally helps everyone I know what a pain freezing in your truck at 5 am is. Namaste!