Automotive Air Conditioning Information Forum (Archives)

chywly555 on Sun May 22, 2011 10:49 PM

Year: 2005
Make: GMC
Model: Serria
Engine Size: 5.3
Refrigerant Type: R-134a
Ambient Temp: 90
Pressure Low: 42
Pressure High: 205
Country of Origin: United States

Truck as dual AC controls for Driver & Passenger. With both controls set for 60 degrees Pass Vents blow HOT (150deg+) air while Drivers vents blow 45. I had to crimp both Heater Hoses to keep cab comfortable. Even vent air (with AC Compressor OFF) blows hot on pass side only. Evap and accumulator are cold (naturally). Anyone know what is the high failure rate part or control?. I have no trouble codes stored but only have a DIY ($100) scanner.

Dougflas on Sun May 22, 2011 11:33 PM

I remember a while ago this sympton may be due to a low charge. Not sure if it was driver hot passenger cold or visa versa. You may wnt to pull the charge and recharge to specs.

HVACNY on Wed May 25, 2011 12:44 PM

Either you have a vacuum leak which is not closing your blend door,or your passenger blend door is broke and stuck open,forcing all the air on that side over the heater core.They sell kits to fix it.One you have to remove dash,the other you cut through the glove box right next to the evaporator..Look in your owners manual on how to run the diagnostic codes for your hvac system to know if the blend door is broken for sure.Hope this helps..Tom

Edited: Wed May 25, 2011 at 3:04 PM by HVACNY

NickD on Thu May 26, 2011 7:58 AM

Start with the basics, heater core inlet and outlet hoses should feel red hot to the touch and the evaporator inlet and outlet hoses should feel ice cold with the vehicle warmed up and the AC running full blast. If you don't have this, these problems have to be cured first.

Then you look into the automatic climate control circuits. This is easier said then done. Can speculate on the problems, last time with ATC found the small hole in the dash that feeds at tube to the in-car temperature sensor was loaded with debris preventing that thermistor from working. Hose terminates in the blower circuit upstream so draws a vacuum that sucks in all kinds of debris from the interior. So just cleaned the hose, but had to remove the entire dash to do that. But then it worked fine again.

Debris can prevent proper operation of the mode or blend doors, if it doesn't break those little plastic gears first or if the doors aren't warped. Kind of insisted on having ATC in all of my vehicles, but finally occurred to me, is this really a convenience? Already had trips over 300 miles from home was either baked alive in the summer or darn near froze to death in the winter. Totally helpless, can't even turn the darn things off, strapped in a seat anyway, and not that inconvenient to make minor adjustments with a far simpler manual control system, and with a manual system, you do have some control. Already passed up to huge discounted new vehicles with ATC, have enough problems.

But that is just my personal opinion, have fun trying to find your problems and repairing it, better get a manual,