1999 Plymouth Voyager: the heat comes out of the defrost vents only, even when I turn the knob to floor vents. Any ideas on what the fix is?

Most likely the air flow diverter/blocker isn't moving. Can it only blow from the dash vents or can you get floor heat as well? If not then most certainly that is your problem and if it's never been serviced it may need replacement. Good luck!

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Oct 13, 2011 - 30 posts - ‎21 authors
It will not switch into upper vent mode, only have the option to have it all on my ...You mean the switch itself on the dash will not turn physically?

Turning vent knob (defrost, mix, dash,floor,etc.) has no - Fixya

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Turning vent knob (defrost, mix, dash,floor,etc.) has no effect. Posted by Jim Long on Jan 01, 2016. Want Answer 1. Clicking this will make more experts see the ...

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3) Mode of operation knob has no effect (air comes only to floor for example) 4) Rear defog ... The transistor is MPSA56 (bipolar pnp) and you can locate the faulty one easily. It is the .... With the switch turned only to Vent, no air from anywhere?

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Sounds like the item got caught in the blend door between the heater coil and the condenser. Unless you can snake something down the defroster port to snag it, the only way to get this fixed is to remove the vent box from under the dash. In most vehicles this requires removal of the entire dashboard, draining of the cooling system and evacuation of the A/C system before the box can be removed and opened. Sorry for the bad news.

U have a vacuum leak so all of your controls for vent defrost floor etc. will work but intermittently or once in a gray moon this is so hard to explain because to fix this is not going to b a five minute job try atleast 5-10 hours of trial and err you have to track down the leak and I guarantee there is more than 1 regards Chris

Couple of possibilities here. One is the heater core bypass valve that allows the coolant to flow to the heater core. Make sure that the vacuum tube has not come off of it. Should be under the hood just on top of the blower motor assembly. Let the engine get hot and check to see if the hoses going to the heater core are getting hot coolant flowing through them.

Does the air flow through the defroster, front vents, and floor vents when they are selected? If not, this can indicate a vacuum leak on the HVAC control panel or a failure of the switch.

sounds like you have a broken vacuum hose for heater controls or vacuum reserve tank if controls changes when accelerating or going up steep hill, check your vacuum hoses from engine to inside controls

sounds like tou have the blend air door motor bad located on the heater box under the dash

try ur ac in dash filter ive had that problem b4 but ur core is under the hood pass side big black box thing,couple bolts it should split in half or off firewall

There is a vacuum leak under the hood. Find the vacuum line on the passenger side where it comes through the firewall and follow it to the engine. You system needs vacuum to operate and without it the default setting is on defrost for safety reasons.

i had a simmiler problem on my 95 chevy pick up. on mine it would not chg. from floor to defrost, no matter where i put the selector. with mine it was the controls. if you go under solutions for k1500chevy gmc trucks it should tell you what your problem is, or give you an idea whats going on with yours.