Need some help with the crazy AC/HVAC system

[Scott06HEMI]

2011 Ram 1500 4wd Laramie with auto-climate controls...
So a few weeks ago my AC started acting weird. When you first start the truck and the AC comes on, it would either start off blowing on high or on low (either or). Then for the next 5 minutes or so it would stay on this speed regardless of the temperature setting. At this point you can not manually adjust the speed, what ever it started on it stays on. If I change the vent settings from auto to manual, the vent selection does change (ie from face to defrost to feet it adjusts normally). However the speed will not change no matter what I select. Then after several minutes (I have not timed it), the speed will suddenly change and at this point I can adjust the speed manually and it seems to work fine. I have ran codes and don't see anything in the body control module, I have changed the blower motor resistor (no change) and tried changing the blower (no change) and combinations of both (old resistor/new blower motor, new resistor/old blower motor, etc). At this point I don't know what else to try. Anyone else run into this issue before?

 

[moist_oyster]

You could probably find a HVAC control on eBay for decently cheap to try out. you could also try recalibrating the system by putting both knobs in auto and holding the recirculation button for about 10 seconds, let go, then hold it again until it starts to blink

 

[Scott06HEMI]

I tried the recalibration process and while it did go through the process (thanks for tellinbg me how to do that), it did not fix the issue. So I have swapped, blower motor, blower resistor and did the recalibration. Any other thoughts other than swapping the control module.

 

[rzr6-4]

There are two kinds of people: Those who prefer manual controlled HVAC systems and those who are wrong. I have never been in an "auto" system that I didn't absolutely despise. If its already 70deg outside ya it works fine but it's hard to screw up already nice conditions. If it's actually hot or cold out, they NEVER do what I want them to. And you can't always override it to do what you want either. I was in my dad's Sierra and I had it set to 85 and it was still blasting cold air. It was an hour drive so I was pissed off at the system for that entire trip.

I have nothing to actually contribute here, just my ******-rant for the day. Thank you for coming to my Ted Talk.

 

[Scott06HEMI]

So adding to this mystery...
I have noticed that the AC will allow me to change the speed after several minutes. I decided to time it and all 3 times I did, it took right at 5 minutes and 30 seconds for me to get control over the blower speed. It did not matter if it was on auto or if it was on manual. Still don't know what is going on.

 

[StateOfMind]

Scott, I have recently been experiencing a similar problem. 2018 1500 2wd bighorn with auto climate. I'll get in and occasionally it'll be locked biggest heat setting. I cant adjust temp or blower motor, trying to take it out of auto doors nothing. Naturally, this has tended to happen on 90 degree days with the interior of the vehicle already at broil. Turning the truck off and on again didn't even change it. I found it I go in to the radio climate settings and turn off the vacuum, I can get back control. I wonder if our situations are caused by a common issue?

 

[chri5k]

Has it been particularly humid? I believe that system has a humidity sensor in addition to a temperature sensor. In high humidity conditions, it will run the A/C on high with recirculation to lower the humidity in the cabin.

 

[Scott06HEMI]

Mine is a 2011 so it is before the big radio head units that control all the settings. As for humidity, I live in southern Louisiana so pretty much every day is extremely humid lol. I haven't had an issue with the temperature however, but I haven't adjusted it from 68 degrees since winter. I think it could be the infrared temp sensor in the overhead but other than ordering a new one and giving it a shot I can't really do much to test that.