AC blows out the top defrost vent and floor vent...the switches back?

696

696

Active Member
Joined
Jun 11, 2009
Got in my car today and kicked on the AC. It was blowing out of the defrost vent and the floor??? After awhile it "switched" and started coming out of the dash vents. What to I need to start to look at?? Cables need adjusted or lubed?? Everything is smooth with no binding.
 
I believe these cars are notorious for this. They have a vacuum block that runs all the vents and they like to come loose which will cause slow reaction to changes when the levers are moved. if you pull out the heater controls they are just attached to the back. if you ever hear a vacuum leak sound on the interior of your car and wondered why, this is it. I say "i believe" because ive never had it happen to me (knocking on wood) but ive read a lot about this happening. sorry i cant provide more details but im sure someone else will be able to soon! HTH!
 
If it just did it once one of the doors might have just been stuck from not using it often.
 
Maybe, it worked the FEW times I checked it but yesterday was the 1st time it blew out the defrost and floor. I tried switching from floor to defrost to vent to max but it didn't help. Finally left it on max and it started working. I'll keep an eye on it and see.
 
You know, that's EXACTLY what happened to my '88 Jeep Cherokee, air only comes out of the defrost, though, no matter what position the switch is in...

I followed what you just stated, pulled out the switching assembly, checked all of the vacuum hoses for leaks, disconect, but nothing....still vents out of defrost...

So, it comes to mind that it just may be a check valve under the hood, as this Jeep has one down by the blower motor.....this may be the problem, though.

Well, just an idea that could be applied to a Turbo Buick....:rolleyes: If the above doesn't work, please forget what I said....thanks.:)

Bruce '87 Grand National
 
Vaccum switches are still avaialble and cheap. If that not it the servos which are vaccum operated maybe be boundup by a stickey door. I have had several cars do this some worse than others. One would stick then bang sound like a gun went off and start working again.:smile:
 
Mine too... :-(

My air controls are doing exactly the same thing except they don't fix themselves after running.
Took it to Buick and they converted the AC to the current freon and found a couple of vacuum hoses that needed attention.

They said it worked perfectly...and even did the temperature check using the vents (55 degrees...not bad for a 25 year old compressor). I picked up the car last night...no air flow out of the vents and the service guys were already gone. I called them today but they couldn't look at it....ba$tards....so I will have to take it back during the week. They did let me talk to the tech and he walked me through his work and it looks fine.

I took the climate controls out of the dash and everything looks hooked up, and not pinched. I even tried the vents with the controls hanging out of the dash just in case they were getting pinched after cramming everything back into its small space. I'm stumped but I'm not that great of a mechanic so its a familiar feeling! :redface:

SteveV mentions vaccum switches but I don't know where those are located on the car. I could take it back to Buick and probably will but wanted to take a swing at it myself do avoid the hassle.
 
Dash65 said:
My air controls are doing exactly the same thing except they don't fix themselves after running.
Took it to Buick and they converted the AC to the current freon and found a couple of vacuum hoses that needed attention.

They said it worked perfectly...and even did the temperature check using the vents (55 degrees...not bad for a 25 year old compressor). I picked up the car last night...no air flow out of the vents and the service guys were already gone. I called them today but they couldn't look at it....ba$tards....so I will have to take it back during the week. They did let me talk to the tech and he walked me through his work and it looks fine.

I took the climate controls out of the dash and everything looks hooked up, and not pinched. I even tried the vents with the controls hanging out of the dash just in case they were getting pinched after cramming everything back into its small space. I'm stumped but I'm not that great of a mechanic so its a familiar feeling! :redface:

SteveV mentions vaccum switches but I don't know where those are located on the car. I could take it back to Buick and probably will but wanted to take a swing at it myself do avoid the hassle.
Click to expand...

They are on the head that you had hanging out of the dash.
 
Found the culprit

The Buick tech who converted the A/C and "fixed" the vent problem put the check valve in backwards right before the T connector at the EGR / HVAC-Cruise Control split. After I got my hands on the vacuum line diagram, it wasn't too hard to figure out. Thought the check valve was bad until I blew through it and figured out the guy put it in backwards(I'm not an experienced enough mechanic to know the white/black color orientation by heart).

The silver lining is now I have nice cold A/C blowing me in the face and a $50 credit at Buick!:)
 
I had a strong feeling it was the check valve that I mentioned...glad you found the problem. I replaced the check valve just below the heater blower in the engine bay on my Jeep and that solved the problem.

Bruce '87 Grand National
 
Just to clarify you've made sure you have good vacuum on the HVAC line and the line to the heater control valve isn't leaking?
 
Nope, not 100% sure I checked THOSE line where are each located and I'll check'em.
 
There are 2 hard plastic vacuum lines that exit from the heater box by the blower motor. One runs to the heater valve on the hose going to the heater core and one runs over behind the intake and connects by the egr check valve. If you don't have the second hooked up the box will be on defrost all the time. If it's hooked up but the check valve is bad the controls will work when vacuum is available but will blow on defrost when there is no vacuum. (like under acceleration)
 
Ok I'm confused, I thought it was working now and that it only did this once?
 
Collin, It has continued to do it now. If you drive it (make vacuum) it will switch after 10-15 min. Sitting with the car on but not running it wont.
 
If the car isn't running it never will switch, but it should definitely happen faster than 10-15 minutes...Does it still bang when it switches, or does it switch normally just take a long time?
 
You must log in or register to reply here.

Similar threads

H
No start. Losing motivation.
2
Replies
22
Views
3K
phil_jordan
P
L
AC not blowing on high and not blowing thru center vents
Replies
5
Views
995
l3lue
L
T
Ac question..
Replies
2
Views
474
salvageV6
salvageV6
8
Air only out of top and floor no dash vent
Replies
9
Views
1K
No disintegrations
No disintegrations
M
Heater control valve question....
Replies
5
Views
2K
TurboTGuy
TurboTGuy
Top