creaking noise in dash, ac blows warm

[bh06exp]

My problem started a few weeks ago, i have an 06 explorer limited with the dual zone ac. With the ac on i will occasionally get warm/hot air out of the passenger side vents. Before this happens sometimes i hear a creaking sound from behind the dash. Sounds like a vacuum leak. Its definitely not a popping sound like i have read in other posts about the blend door. When its does blow warm it lasts any where from a few seconds to a few minutes but has always returned to cold. Any help would be greatly appreciated.
Thanks
Brian

 

[08Exploder]

If you have a vacuum leak the reason why it's going cold and warm is because there is a vacuum switch on the heater hose going to the heater core it shuts the flow of hot coolant to the core of you have a vaccum leak or bad switch it could be open while on cold first thing I would check is the check valve in the engine compartment take it out and blow in it you should only be able to blow on one side of 2 sides replace it and see if still problem if problem persists look for a vaccum leak or put a gauge on where you disconnected the check valve from and see if it holds vaccum if not then you have a leak somewhere under dash.