the driver side blows cold air when it is set to warm on 2008 Mercury Mariner

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why does the driver side blow cold air ,when the temp setting is on warm?
(4) Answers
Chances are there is a problem with the driver side temperature control actuator. Your 2008 Mercury Mariner may still be under warranty for this. Perhaps a trip to your local dealer would be in order.
I went to the dealership for this. I had this problems and audible clicking coming from the dash. They told me the air vent motor was going out and would have to be replaced. First response I got was this was not covered under warranty and would be $400 to replace.
Mine did the same thing on an intermittent basis. The problem was the blend-doors (Dual Zone Climate Control) which were replaced and now works perfectly.