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Blower motor on high speed and no air flow out of vents


redsled2007

Question

I have a 2007 Sierra Denali with climate control. My problem is after about 45 minutes of driving, with the air conditioner selected. the blower motor speeds up like it's trying to catch up. Then I notice that there is no air flow coming out of the vents. I try manually selecting vent, floor, or defroster. I here them change, but no air flow out anything.

If I turn off the truck for about 15 minutes then start driving again, everything is ok for about 45 minutes, then it starts all over again.

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If you can hear the blower motor running, it is possible that if the humidity is high, the evaporator core may be icing up and blocking airflow. With the system off it gets a chance to thaw out and the blockage melts away. This can be caused by overcharging the system. Check this thread out http://www.gm-trucks.com/forums/topic/117238-air-conditioning-advice/

You may be on to it. It happened again yesterday, so I stopped the truck and checked the evaporator cooler and seen that it was covered in frost about a 1/4" thick along with all the lines leading up to it and out.

Unit has never been serviced since new, so I'm thinking a little low or the accumulator pressure switch is bad. (No problems with cooling temp)

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The air flow issue is like a door has closed some where.

The whole dash was replaced a couple of months ago due to cracking by the air bag along with the climate control unit (lights burned out).

The reason I say it's like a door, when I restart after the air flow problem, the blower starts up with no air flow for about 1 second, then air flow.

The pass side of the controller does not shut off the pass side like it used to.

Yes, I took it back to the dealer who did the dash and they said the controller would not do this. BUT, they were aware of this issue and could "Fix" the problem with a modified program from GM.

It would ONLY cost me $175 to reprogram the BCM , and it WAS NOT covered by my warranty!!

Before I shell out $175 on something that I think should be under my warranty, I'd like to here from some other folks.

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If you can hear the blower motor running, it is possible that if the humidity is high, the evaporator core may be icing up and blocking airflow. With the system off it gets a chance to thaw out and the blockage melts away. This can be caused by overcharging the system. Check this thread out http://www.gm-trucks.com/forums/topic/117238-air-conditioning-advice/

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