HVAC issues

[n0useforaname]

Ok. I'm trying to figure this all out but have a couple questions. Right now my air only blow to the defrost... and sometimes the passenger side is colder than the driver side. My HVAC unit itself also randomly kicks on the AC snowflake.. I dunno. I'm going to start with replacing the actuator on the drivers side that controls the mode.. then go from there. Here are my questions though...

1. Can the mode door actually cause hot/cold issues? Or is it strictly for where the air is forced to only?
2. Do ALL actuators being installed need calibrated? As in pull out the HVAC 1 fuse and the HVAC/etc.. fuse for a couple minutes and put them back in?
3. Does the actual HVAC unit need programmed if I change out the actuators?
4. It seems like Google is showing LOTS of people who messed with their batteries or installed a stereo/etc... and they all have these things go bad. Is this just a Hummer thing? I had a 2500 silverado for 7 years, and I constantly messed with the battery/etc.. and never had an issue.
5. What exactly is the circulation door for?

 

[alrock]

What type of vehicle, an H3?

I can tell you this much from experience:
The calibration mode moves all of the actuators in the system. The calibration process can be started manually but also occurs with the disconnecting and reconnecting of the battery. I've done this process a couple of dozen times in troubleshooting when trying to figure out the all cold/ all hot issue that Hunner demostrated can be fixed with a resistor soldered in.

You do not need any programming beyond the calibration if you put in a new HVAC control panel. I've swapped them out in my troubleshooting.

Calibration of the actuators:
Turn ON the ignition with the engine OFF.
Turn the Temperature dial all the way to the right.
Turn the blower control dial all the way to the right.
Turn the mode position dial all the way to the left.
Simultaneously press and hold the A/C and Defrost buttons until the LED's start to flash.
Once the LED's stop flashing, calibration is complete.

 

[n0useforaname]

I have an H2 with the dual zone digital stuff, so that won't work. Last night I bought a brand new actuator and put it in.. I had the fuses pulled and did the calibration thing.. the actuator started turning clockwise.. then after it hit the tabs to go to defrost mode.. it just stayed there like the old one. I'm thinking it might be the control head or something else now. All I know is I typically have pretty crappy luck, so it will probably cost me a grand to fix this in the end I just remember someone telling me that if there is an "issue" it will default to defrost.. so I probably have a short or something with my luck.

 

[n0useforaname]

Well, in short the dealer had to do a recalibrate with the Tech II... nothing else would work. They said I did everything 100% right, but sometimes that's the only way.. and they tried everything else first too. Either way, $28.36 out the door ain't bad.

 

[n0useforaname]

So they did a calibration update for my H2, and got the new actuator.. worked all day yesterday and then this morning.. BOOM. Broke again. I'm clueless.. and after tearing apart my dash, I've established that this was a problem prior.. The actuator I took out was not OEM... and the control head was dated 2010... And so far it seems like all the other actuators are working fine, and wiring too.. where do I go now? As of late it seems like my passenger side blows more air than the drivers side.. and sometimes the temp will be off from what I have it set to. Can a stuck blend door cause the mode to malfunction?

 

[Big2dabank]

I had to have my AC control module re flashed last year by the dealer, because it was acting pretty screwy and it fixed my problem. May not be your problem, but something to look at.

 

[n0useforaname]

Just an update.. NO ONE can figure out the issue. Actuators were replaced, Tech II scans were done, BCM tested and reflashed, wires checked, grounds/power checked, and even replaced the Control head.. STILL not working. Since I run defrost/floor 99.9% of the time, I just set it there and pulled the power on the actuator. Fixed..