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Discussion Starter #1
Do the duct door actuators work off 12V power or vacuum? I had the compressor replaced late last year and I have noticed over the last couple of months that after having the A/C on for approx. 30 minutes that it virtually quits blowing air out of the vents. I've had it back to the shop twice and they have yet to fix it. I think that if it's vacuum controlled that I have some cracked or unattached tubing. ???
 

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It would be far more likely that the evaporator is freezing than a door actuator decides to move. The actuator would redirect air and not shut it off as there is no door that closes fan supply. If the evaporator temp probe is faulty or if it is no longer placed correctly that leads to evaporator freezing. In t hat case if it is not blowing and you stop and shut it off there will be a much larger puddle of water than is normal. If you turn off compressor for 15 minutes with it not on max or recirc and then back on and it blows that is also evidence of frozen evaporator. When it is happening if you pull over and leave it running the larger line at firewall will usually be iced over.
 

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Discussion Starter #3
I failed to say that when it quits blowing through the vents, I can still hear air blowing somewhere, it's just not coming out of the vents.

Would the condition you are describing be a result from low freon?
 

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You have a vacuum leak or a hose that has a crack in it. When the hose gets warm it may sag and open up the hole. I would check all the vacuum hoses. There is also a vacuum pump that may be going out. Look there also Do the easy stuff first before you spend money on parts that may not be broken. Don't open the system that will cause more problems than ti will fix. Sounds like a blend door not working correct.
 

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The HVAC system changed in 2008 to a no vacuum system. 2007 and down have air distribution and recirc using vacuum servos and temp using electric actuator. In 2008 the whole system moved inside vehicle and uses electric actuators for all purposes.

Automotive systems usually don't freeze from low charge like the high pressure refrigerant home systems do. Far and away the biggest reason is evaporator temp probe problems on that system.

To be sure, you need to see that it is not blowing out defrost vents as that is another problem. When evaporator freezes you hear fan aand often the noise is louder but no air gets through as the evaporator is in the air stream for ALL air that leaves the blower motor housing.
 
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