Of all the irritating problems you can encounter with the operation of the computerized HVAC systems in your Chevy Suburban, this one has got to be: 1) the most irritating, and 2) the easiest to fix.
On Friday the 13th, I awoke to find that my battery could no longer turn over my engine. I jumped it with a spare battery from my garage to get the car started and get my kid to school, then went straight to my local parts store to get a replacement for the battery, which was actually still under warranty. At that point, I didn't notice anything unusual about the operation of the AC system (because it was still early in the day and the outside temp was still cool), and everything else was working normally. Later in the day, however, I noticed that the AC system had gone haywire. The front fan was only blowing from the defroster vents, and the rear AC was only blowing hot. I naturally assumed the worst ... something had gotten "fried" when I jumped/replaced the battery, etc.
My first suspect was the "actuator" (a self-contained, DC servo motor that controls the air distributor flap in your front AC distributor box). I located the actuator (mounted on the driver side of the air distributor box, just above the accelerator pedal), removed the cover, and watched it working. I tried manually forcing the assembly into the matching position on the dashboard control (I don't recommend you try this ... you could end up damaging a perfectly good actuator), only to watch the servo move the assembly right back to the defroster position each time I re-started the AC. Since the servo was responding (sort of) to the dashboard climate control module, I figured the module was probably working right, and the actuator had to be bad.
However, before committing myself to purchase of a new actuator (about $55 on gmpartsdirect.com), I kept digging on the internet, and found another possible solution, which turned out to be the right one. Apparently, when power to the climate control system is interrupted, as when you replace a dead battery, the system sometimes fails to re-calibrate itself properly, which results in the actuator gear assembly traveling to, and sticking on its farthest "default" position ... the defroster vents. This mechanic suggested disconnecting the battery for 30 seconds or so, and then re-connecting it, to give the system another chance to re-calibrate. I figured, sheesh, that's a lot cheaper and simpler than replacing the actuator, so I gave it a try. Wouldn't you know it ... I disconnected the battery; re-connected it; re-started the car; tried the AC, and everything, including the rear AC, started working normally again, as if nothing had ever happened.
Don't even ask me exactly how or why it worked ... the answer to that question is way "above my pay grade." I was just so relieved that it DID work that I felt compelled to post this, for anyone else who might have experienced the same problem with their AC system after disconnecting/replacing their battery.
Of all the irritating problems you can encounter with the operation of the computerized HVAC systems in your Chevy Suburban, this one has got to be: 1) the most irritating, and 2) the easiest to fix.
On Friday the 13th, I awoke to find that my battery could no longer turn over my engine. I jumped it with a spare battery from my garage to get the car started and get my kid to school, then went straight to my local parts store to get a replacement for the battery, which was actually still under warranty. At that point, I didn't notice anything unusual about the operation of the AC system (because it was still early in the day and the outside temp was still cool), and everything else was working normally. Later in the day, however, I noticed that the AC system had gone haywire. The front fan was only blowing from the defroster vents, and the rear AC was only blowing hot. I naturally assumed the worst ... something had gotten "fried" when I jumped/replaced the battery, etc.
My first suspect was the "actuator" (a self-contained, DC servo motor that controls the air distributor flap in your front AC distributor box). I located the actuator (mounted on the driver side of the air distributor box, just above the accelerator pedal), removed the cover, and watched it working. I tried manually forcing the assembly into the matching position on the dashboard control (I don't recommend you try this ... you could end up damaging a perfectly good actuator), only to watch the servo move the assembly right back to the defroster position each time I re-started the AC. Since the servo was responding (sort of) to the dashboard climate control module, I figured the module was probably working right, and the actuator had to be bad.
However, before committing myself to purchase of a new actuator (about $55 on gmpartsdirect.com), I kept digging on the internet, and found another possible solution, which turned out to be the right one. Apparently, when power to the climate control system is interrupted, as when you replace a dead battery, the system sometimes fails to re-calibrate itself properly, which results in the actuator gear assembly traveling to, and sticking on its farthest "default" position ... the defroster vents. This mechanic suggested disconnecting the battery for 30 seconds or so, and then re-connecting it, to give the system another chance to re-calibrate. I figured, sheesh, that's a lot cheaper and simpler than replacing the actuator, so I gave it a try. Wouldn't you know it ... I disconnected the battery; re-connected it; re-started the car; tried the AC, and everything, including the rear AC, started working normally again, as if nothing had ever happened.
Don't even ask me exactly how or why it worked ... the answer to that question is way "above my pay grade." I was just so relieved that it DID work that I felt compelled to post this, for anyone else who might have experienced the same problem with their AC system after disconnecting/replacing their battery.
- mwietstock, Santa Barbara, CA, US