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Why does my 99 Tahoe rear air blow hot

I have a 1999 Tahoe and the rear air blows hot. Front air blows cold. But there is two lines under the hood that looks like aircondition lines sets under the air conditioner tank that the aircondition lines from the air conditioner pump goes to. Can anyone give me any idea what is wrong and what these lines go to.

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If your air works in the front the problem isnt with the air conditioner its in the duct work . There are vent ducts that have flaps that open and close to direct air. If the flapper are not working the air is blowing in from the heater core and you will get hot air . The only solution is to follow the vents back through the truck and see if you can find the flapper and why its not moving. Hope this helps .Good luck and good hunting

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I had a similar issue with my Suburban there's a air blocker that opens and closes between the heater core and the condenser for the air conditioning. Its a matter of getting under the dash and finding the flap . in my case it was an air line that had a hole and wouldn't activate the flap. it runs on a vacuum

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adam r will be eternally grateful.
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