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I don't drive our '09 often, but happen to have it over the weekend. I noticed the air coming from the vents in the rear is cold when the temp control is on full heat. The front temp control is also on full heat, the rear controls are enabled at the front, I checked anti-freeze level and it is full.

I did a search on here to see if anyone else had a similar issue, but had only two hits and they were no help. Thought I would see if anybody else experienced this?
 

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I'm having the same exact problem. Did anyone find a solution?
 

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I'm having the same exact problem. Did anyone find a solution?
Welcome to the forum.
Looks like someone didn't come back to post the repair. That happens often. Year and build (trim level) of your Acadia?
 

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Wild guess. Is it below freezing? Any chance the rear HVAC lines are frozen? Maybe I'm wrong, unsure of the design of these for the rear HVAC
 

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Wild guess. Is it below freezing? Any chance the rear HVAC lines are frozen? Maybe I'm wrong, unsure of the design of these for the rear HVAC
Heater lines would be (should be) full of engine coolant (anti-freeze).
 

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Heater lines would be (should be) full of engine coolant (anti-freeze).
Should be is exactly my point. :) It is a 9 year old vehicle, there's a chance...
 

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Slim to none in my book. ;)
Are the to-rear HVAC lines a separate entity? And are they the same lines for both heating/cooling?
In my previous mini-van it seems they were separate. They burst while driving, spewing the antifreeze in a huge whale tail behind me down the highway. Yet the van drove just fine.
 

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Are the to-rear HVAC lines a separate entity? And are they the same lines for both heating/cooling?
They're in a 4-tube bundle running along the bottom of the vehicle on the passenger side. one inlet/return pair for the A/C, one pair for the heater (at least on the Lambda platform).
 

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And there's probably a check valve at the compressor end in case one blows... or freezes, no? I'm not questioning you, just curious and trying to find a solution for the OP.
 

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Just my .02. Cycle the rear heating control through all the temp range, and modes. I had an issue with my 08 where the upper vents blew cold, sometimes even after the warm coolant should have been warming up the rear. I had to cycle through all the settings and then it got warm.
 
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