After taking my H3 to a shop to evacuate Freon from system that they said was overcharged when I've never had freon put in it since owning it, the AC still had issues . It was cycling the clutch on and off to much and would cycle off for up to a minute and 15 seconds which caused warm air to blow . I found that the pressure sensor / switch was not passing the continuity test so replaced that . Then because they told me that AC only worked on one setting and that was the third coldest . Wanted to charge me for a new module but I had one myself so put it in and recalibrated it and AC now works on all settings.Here's the thing it's doing something that I've never seen before and I'm almost 70. It will blow cold air and then suddenly the vents will all close and I can still hear the fan running and a minute or so vents open back up and sometimes its cold air but other times its just cool air. It does this back and forth. I just replaced AC ambient air temp sensor , which took me a while to even find that little critter on a bar in front of radiator . It pops in from the other side of bar so you can't see it from the grill and finally I chased a wire to back of bar and noticed a little black button looking thing and pushed it out and there it was. Have not driven it far enough to know if that changes anything but will let you know. Hoping someone has more about this than I know as to what can cause this issue, I've googled it and found no symptoms like that at all. It's a Hummer , right !!!

 

Did you ever have the HVAC recall work done?

Might want to review and do the calibration again.

 

No to the recall work , I've only owned it 3 years and only driven it about 5,000 miles and it only has 97,000 miles on it . I did a recalibration of HVAC module when I put in a used one as mine was only allowing AC to work on one setting which was three clicks up from coldest, it works on every AC setting now, I just today did recalibration as it seems like the recirculation button on the fan is turning on and off as the vents shut open and closed. It actually got worse today as I was trying different things to see if it changed anything and it's weird to me but as it is blowing warm air I turned off the recirculation button on fan and cold air started coming out vents. Then I turned off the button that activates the AC when fan is on and you are on cold side of temperature control and turned the button on for fan again and it blew cold air just the same . I just turned off AC button at temp control and turned on button at fan and heard AC clutch cycle on and again cold air. It's now blowing warm air way more than cold and I noticed that the low pressure line is iced up. I also just now had a really strange thing happen . I thought maybe engine was running hot so I ran it with a scanner on it with live data that shows temperature and it was not running hot but what did happen was fan would not come on at all under any setting , I tried heat even with AC and recirculation all off , then after running it maybe 5 miles the fan came back on in all speeds. That's why title is freaky AC issues , can't figure it out. What is funny is Hummer never had any AC issues until I had a shop diagnose why the blower motor stopped working after I replaced the temperature control actuator and it did an automatic recal when I put key back in ignition after install. None of the ***** were in proper place and fan was on 2 and never came on again . I ran power to fan and it worked fine but couldn't figure it out motor was good , resister was good and relay was good , I thought PCM was not appling the ground to complete curcuit. GMC doesn't let you have or buy PCM pinout.It turned out to be a short at firewall and AC issues started the day I picked it up from shop.

 

Get to the point instead of writing a book!
I pulled the above from your long posts> Just to be clear, the vents are manually operated where as the duct BLEND DOORS are powered.

 

Thanks Hummerz for your reply and I am sorry for long message however I wanted to put some history of things done on Hummer. I have already done recalibration of module now twice and does not change anything . I do know how vents and blend doors work as I have changed one actuator on Hummer back a year ago for temperature control door. Those three actuators as far as I know will not close all vents off at same time when fan is on and I tried turning temp to heat but still no air from any vent as I hear fan motor still running . What I have discovered is there is a separate actuator for recirculation and it is in a housing behind glove box. The housing covers the evaporator temp sensor , the recirculation actuator , the air inlet and possibly the cabin filter. Problem is they (GMC) act like this housing is invisible when you look at diagrams in repair manuals like the Schwarttzy . So far my inspection only came up with two bolts at bottom of housing behind the metal flat bar that glove box is bolted to , had to take those out and can only feel the head of bolts and will only take off 2 inches of this housing , Will post what I find for future reference, my back is already hurting just thinking about doing this as there is little room and very uncomfortable as I remember from blower motor diagnosing last year. If anyone has taken this housing off please advise as any help is better than no help .Thanks

 

H3s don't have a cabin filter.

Good luck.

 

Thanks Doc, I wasn't sure that it did but my manual and every time I google for answers on H3 AC it gives filter has one of the things to check . You would'nt also know how to get into the housing under dash behind glove box . It has the evaporator and actuator for recirculation hidden inside of it . Thanks again

 

I'd like to know this as well. My Recirculate setting doesn't close off outside air completely (it did in the past). How to access that actuator is the question.

 

Well in both of my Hummer repair and shop manuals it acts like the housing that I see when I remove glove box is invisible . It shows the actuator at the top just under surface of dash plus the air inlet . Also the Evaporator Temp. Sensor is right there . Only screws I see are two at the bottom of this housing going upward and looks like those will only remove a small cover at bottom leaving the rest of housing remaining which is about 12 inches more box. I don't see any other bolts or screws that allow housing to be removed . I was going to start with taking cover off and go from there but I think now I'm going to take it to another shop and see if either of the items (actuator, Evap. Temp sensor) could be the culprit before I waste time trying to figure out the housing removal. I will say it seems like GMC intentionally made it hard to access these items or they would have instructions on how to remove this housing.If anyone has conquered this housing I wish they would let me and you both know how they removed it.Thanks