2004 Pontiac Montana blows hot and cold thru vents even though the air conditioning is on. Mechanic says have to take whole dash out to get to the vent doors to fix it. Is there any other solutions?

SOURCE: Heat wont blow through heater or defroster vents

common problem, check under dash by the gas pedal if control arms are muving went selecting from ac to heat cuz this it is the control for the vents to go from ac to heat and to defrost.

SOURCE: even when air is off, hot air comes out all pass side vents

it is the flap door inside the heater box area.alot of gm with electronic climate control have the problem.there is an actuator motor that needs to be replaced.

Harvey N Tawatao

• 3854 Answers
• Posted on Aug 22, 2009

SOURCE: 2000 pontiac montana air conditioner driver side

That is correct, the air blend door actuator. "flapper valve" may need to be replaced or cleaned and free from binding up. Good luck and hope this helps. If there is an Auto Zone in your area, they can order the part you need and give you the step by step instructions to removing the old actuator and replacing it if it's damaged. Good luck and keep me posted, be glad to help. 

SOURCE: heater only blows hot air

This is my best guess with out knowing the year of the vehicle.
If you have a climate control system, ( driver's side, and passenger side heat & a/c setting ), you likely have an issue with the blend door being stuck, or a bad actuater, ( this moves the blend door )

If you do not have a climate control system, you likely have a trap/flapper door sticking, or some blockage in the duct work.

I hope this helps you.

Testimonial: "it is a honda crv 2003. how do you unstick the flapper?"

SOURCE: air conditioning not blowing thru the vents

There is a black vacuum hose in back of the glove box toward the top connected to a gray hose about 1/8 thick.You need to check to see if there is vacumm there.If yes then you need to take the bolts off to be able to tip the dash back enough to see all the vacuum hoses.Make sure they are all connected.It was alot of bolts but its is the best way.I had a hose off going to one of the acuator doors.Glued it back on and works great