Fan only blows heat

[ScottInOKC]

My 99 Explorer is only blowing heat despite what I set the temperature. The A/C does blow cold mixed with the hot air. The other day, I noticed a flapping sound coming from the passenger floorboard area, so I'm guessing a damper/louver is stuck open/closed.

That having been said, I don't have the first clue where to start looking to diagnose and fix the problem.

Thanks in advance!

 

[koda2000]

your blend door is broken. this is allowing heat to flow from the heater core into the HVAC system. there's nothing wrong with your a/c it's just being overpowered by the hot air.

there's a cheap fix (which involves cutting a hole in the heater box, behind the glove compartment) and a very expensive, labor intensive fix which requires removal of the dash. with the cheap version, you can replace the blend door or operate it manually getting heat or a/c, but only manually. Dorman offers a replacement blend door. there are many threads (and at least 1 STICKY) on this subject, which give specifics on this problem.

start by removing the blend door actuator and checking it's gear, but the gear on the door is usually what breaks. the noise your hear is the actuator trying to move the blend door.

 

[ScottInOKC]

Thanks for pointing me in the right direction, I'll start doing some research.