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A/c Problem: It Doesn't Turn Off!

johnsonjf

By johnsonjf
in Ask A GM Technician

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johnsonjf Enthusiast

johnsonjf

Posted
Posted

This is an updated repost of an earlier poster that I replied to in which his 2007 Classic series Silverado/Sierra's AC would not turn off.

 

Well, I believe our problems are one in the same (not sure about controls and such). I drive a 4.8L Silverado 900 seies extended cab with less than 1000 miles on it. AC controls have the three knobs with the blue light indicator on the edge. When I am stopped or not in motion and I have the A/C blow-speed knob turned to the off position, the AC is indeed off. However, as my speed increases, the AC will begin to blow once again. I know this is due to the truck moving forward and pushing the air into the ducts. However, why doesn't off mean off?

 

The only way I have found to actually turn off the A/C is to turn the blow-speed knob off and selected in-cab vent circulation as opposed to outside air vent.

 

This isn't too bad of a problem until I get to about 70 mph where, on even the lowest setting, the A/C blows harder than some other A/C's on high (due to the air being forced into the ducts from the forward motion of the truck). This gets me to the point at times where I am freezing my butt off!

 

Are my duct flaps stuck open or something? Or am I stuck having to twist knobs and press numerous buttons to jsut get my A/C to turn off? Am I stuck with an A/C whose air-speed is always dependent on the speed of the truck itself? Does anyone else have this problem and have they found a dealership solution?

 

Thanks in advance for any help you guys offer. I am so glad I found this site.

ZZ327 Senior Enthusiast

ZZ327

Posted
Posted

when you have the recirc button pushed in or knob turned on. It also runs the compressor at the same time. The old ones do it too, I think for defrosting.

 

For no A/C you need the AC knob, and the recirc knob OFF

 

Only the fan on for fresh air or not.

wzy50 Enthusiast

wzy50

Posted
Posted
when you have the recirc button pushed in or knob turned on. It also runs the compressor at the same time. The old ones do it too, I think for defrosting.

 

For no A/C you need the AC knob, and the recirc knob OFF

 

Only the fan on for fresh air or not.

 

I believe ZZ327's coment is true. The only way to shut A/C off is turning both A/C and Re-circulation buttons off. Either of them is on will make the A/C working. As I remenber it is not consistent with the manual book tells. I will go double check it.

Capt.Slim-Jim Enthusiast

Capt.Slim-Jim

Posted
Posted

the recirculation button keeps the a/c running as necessary to remove humidity and stop fogging even when the your not using it for a/c cooling. SAme thing when the defroster is selected.

Always leave the button OFF unless it is too hot outside then it will work as a "Max A\C" like other models

Leaving it off will blow "fresh" air in and will cool up to 25d ~ below outside temp.

With it on it will cool up to 25D below the temp in the cab

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