A/C - Reduced cold Air - very low flow

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[robindcs]

This problem has occured twice since May 2011. Air Conditioning starts off "Normal", excellent flow of cold air. 1 1/2 to two hours into trip the airflow is noticed to be severly reduced and cabin getting warm. Hand on upper vents cold but hardly any airflow. Shutdown for five minutes and HVAC returns to normal with good airflow. Opened hood after shutdown, no icing evident on AC lines. Otherwise a perfect ride with no snags in almost four years. Any ideas gratefully received, not anxious to go back to a dealer as everything else is fine!

[mikemu]

This problem has occured twice since May 2011. Air Conditioning starts off "Normal", excellent flow of cold air. 1 1/2 to two hours into trip the airflow is noticed to be severly reduced and cabin getting warm. Hand on upper vents cold but hardly any airflow. Shutdown for five minutes and HVAC returns to normal with good airflow. Opened hood after shutdown, no icing evident on AC lines. Otherwise a perfect ride with no snags in almost four years. Any ideas gratefully received, not anxious to go back to a dealer as everything else is fine!

Does flow increase if you lower the temp setting?

[robindcs]

No

[gig229]

Do you have a hissing noise when you turn on the AC and while it runs?  If you do, that could indicate the refrigerant is leaking out.  As the refrigerant level gets really low, the evaporator coil will freeze up reducing the flow of air.

[Shadofire]

AC evaporator boxes have a drain that allows condensed moisture to drain out the firewall/bottom of the car, it may be plugged. Check to see if water is dripping on the ground center and rear of the right front tire wheel well. The other problem could be a defective pressure cycling switch that is allowing the ac compressor to stay running too long. This will make the system operate at too low of a temperature which would cause the evaporator to ice over blocking air flow and causing the problems you are having.

[robindcs]

No hissing noise is evident.
Condensation water draining from the forward (firewall) area........
Pressure cycling switch will be investigated.

[AA/78U-Supreme Forum Moderator]

Manual or digital HVAC?  What temp are you running the system?


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[Shadofire]

Lambda platforms use a Thermal Expansion Valve to throttle refrigerant into the evaporator. It is possible that this unit is defective and is allowing the evaporator to be flooded with refrigerant allowing it to over cool.I was actually surprised to see the use of a TXV as opposed to a orifice tube, which is why earlier i mentioned the cycling switch. The temperature of the evaporator is dependent on system operating pressures and possibly the exit temperature of the evaporator as it passes through the TXV. TXV's typically have a bourdon tube that "reads" temperatures in the evaporator to throttle but in this system i cannot see such a tube. Either way, the icing will be independent of the set temperature on the dash as this just governs the air temp by varying the air that passes through the heater core or bypasses it.

[robindcs]

Thank you Shadofire, I will investigate the thermal expansion valve (TXV) as well as the pressure cycling switch.

[frankcal]

Interesting...this happened to me a couple of weeks ago about 1.5 hours into a 2-hour drive coming home from vacation.  About an hour after we returned home, I took the Acadia out to diagnose the problem, and everything was fine. I would be very interested in anything you learn.

Thanks

[robindcs]

AA/78U  Digital/AUTO      Set at 21DegC or 71DegF     Outside air  25DegC or 77DegF   Both sides set the same.

[Swim Dad]

Everyone,

This issue has been discussed on this thread:

http://www.acadiaforum.net/forum/index.php?topic=7818.msg156943#msg156943

Maybe the title did not do a good job of explaining the details of the issue.  Letting the vehicle idle for 15 minutes will thaw the ice and the A/C will work fine.  I have had my 08 to the dealer 2 times for this exact problem.  I even took the dealer pictures of the larger A/C line covered in ice / frost.  The dealer called GM Tech which recommended replacing / recharging the A/C fluid (freon? was a little low) and they also replaced the A/C evaporator sensor.  In my case there was no water in the blower housing as Happy stated in the above thread.

I have not driven the Acadia for an extended time to see if the latest fix has solved the problem.  Have your dealer call GM tech so that they continue to get reports of this issue.