air conditioning comeing out the defrost ?

[fnoblitt]

on my 97 chevy , the air conditioning only wants to come out the defrost or floor vents but not out the dash vents like it's susposed to. this happened to anyone else?

[ChevLoRay]

Yeah. We had an '81 Impala wagon when we had all five kids at home. When going up a hill or pulling hard, a lack of vacuum would cause the flap to move and deflect that a/c thru the defroster vent.

With cfc-linked defrost, it may be a switch that is causing it, instead of a lack of vacuum. Beyond this idea, I'm lost.

[Rodms]

vacuum maybe,these newer ones if something fell through the dash down it will cause all kinds of problems,also turn your controls slow and see if it locates

[fnoblitt]

when i turn off the ac button , then the fan blows wherever i point the knob ,even out the dash vents. i push the ac button in and it comes back out the floor or defrost. so i'm thinking there may be a problem in the switchs ?

[Rodms]

Originally Posted by fnoblitt

when i turn off the ac button , then the fan blows wherever i point the knob ,even out the dash vents. i push the ac button in and it comes back out the floor or defrost. so i'm thinking there may be a problem in the switchs ?

Yeah it sounds like it could be a switch,but check your vaccum lines first

[69-350]

pull your switch panel out, and check the connections. In my 97, the fan speed switch quit working properly. It would usually go all out, or nothing. Which really sucked in the winter, when it's between 0 and 20 degrees, and you have no heat and are trying your best to defrost the windows. And if you moved it just right, it would work properly, for a while.

It turned out, inside the fan speed switch connector, one of the terminals must have shorted, and melted the terminal and the plastic around it, causing it to occasionally contact another wire, thus messing the speed up. It was $25 for the switch at Checkers, and $57 for the wiring harness (the little one cent plastic square piece, and ten wires. Dang dealerships will rape you any way they can)

Anyways, it's really easy to pull it apart, just pop your dash bezel off, push the two clip slider hold down dealies (hah, professional, I know) pull the panel out, unclip the wiring harness, and they're like a 6mm or 5.5mm or some small screws, check all the stuff out. I'm betting it's the switch for the vent selector, probably shorted or something.

[junkman8302]

There are no vacuum lines on the newer trucks. You will be looking at either the contoller being bad or one of the mode door motors being bad. If you have to change the mode door motor, all I can say is good luck, because may have to pull the entire dash assembly out of the truck. I just replaced an evaperator core on one and had to pull the whole dash out, and nearly had to pull the entire steering column out too. If you need help I will check the books at work and see if I can find some troubleshooting and repair directions for you (I work at a GMC Medium Duty dealer) if you want.