AC/Heater vents in 99 Blazer.

[Nandy]

I seem to have either an actuator or a vacuum problem in this vehicle. If my ac is off the outside air still gets inside or the vehicle. I am not talking a small leak, I mean enough air flow to rival the fan speed #1. Also, if I turn the heater on in the morning and i set the fan to speed one I can feel the heated air. Once I get on the road and fast enough, about 40mph the outside air takes over.
The flaps or whatever they are called that block the air and are use to select which intake to take (hot/cold) are obviously not doing their job. I think I have a vacuum line loose but I cant find it. I dont want to take the entire dash down without some insight of what to expect. Being that it is cold enough for me even if I cant fix it right I would rig the "flaps" so the heater works. Right now I drive with a sleeping bag for my legs and a jacket/gloves...
My biggest points are:
Do I have to take the dash down? Can it be accessed from the bottom?
Anyone had this experience before? What am I more likely to find?
Anyone with a diagram will be great.

Thanks one more time.

 

[Tyme2fish]

Re: AC/Heater vents in 99 Blazer.

I have a '97 Mountaineer with the same problem. A "Ford" site helped me with the solution.

Google "Blazer" and go from there would be my answer.
Sorry, that's all the help I can contribute.

 

[Gary H NC]

Re: AC/Heater vents in 99 Blazer.

I have got some good help from the Chevy forum when i was working on my Tahoe,
http://www.fullsizechevy.com/forums/

 

[ne7800]

Re: AC/Heater vents in 99 Blazer.

it could be a vacume line on the back of the control unit i havent had one apart in a while but i don't think you have to take the dash all apart there shoul be a seprate dash piece around the radio and heater controls, the cabin air intake i belive is just below the windshild behind the hood is it possible that a bunch of crap got down in there and is stopping the vents from working properly? do you park by any pine trees? pine needles are famous for getting in there

 

[Splat]

Re: AC/Heater vents in 99 Blazer.

The actuator can be accessed by removing the glove box on the passenger side. I believe on the blazer is the same as my 2000 Blazer/Envoy edition and is actually electronically not vacuum controlled.

Bill

 

[Splat]

Re: AC/Heater vents in 99 Blazer.

Come to think of it, my envoy has the automatic climate control. But if I turn the system off, when cruisin down the freeway I can feel air being forced into the defroster vent, and this makes the cabin very warm. So I never drive with my climate control off. I bought the truck used in 2001 and It's done thet since I've owned it. I'm just used to it by now.

Must be a design flaw.

Bill

 

[Nandy]

Re: AC/Heater vents in 99 Blazer.

I spend time in the woods with that vehicle but I dont usually park it where debris can get to it, but who knows. I did not have a problem when I got this vehicle used in 2001. I did some work a few years ago and had to disconnect a few vacuum hoses. Shortly after that I noticed the changes in the ac...

 

[Tyme2fish]

Re: AC/Heater vents in 99 Blazer.

I did some work a few years ago and had to disconnect a few vacuum hoses. Shortly after that I noticed the changes in the ac...
__________________


Well,there you go.!!

 

[xtraham]

Re: AC/Heater vents in 99 Blazer.

if the control does not change in any position IE: floor, defrost, vent etc. you have a vacuum problem, could be the control or a vacuum line, the vacuum line goes from the intake constant vacuum side to a vacuum reservoir, it's about the size of a softball and black either on the hood or fender well, and should have constant vacuum when the engine is running, when no vacuum the default is normally defrost, if all the positions work it's the vacuum line going to the blend door actuator or the actuator, or as stated above, "something" stopping the blend door from closing

 

[Nandy]

Re: AC/Heater vents in 99 Blazer.

I can select floor, defrost, vent but I always get some air coming of the face vents. Where is the blend door actuator and the actuator? Also, is there a door that should block all air when the unit is off or would that be that same blend door?
Thanks!

 

[xtraham]

Re: AC/Heater vents in 99 Blazer.

remove the glove box and see if it has a vacuum acuator or electric, if it has the electric actuator unplug it, then see if you have heat.
the blend door is between the A/C and the heater core @ the firewall

 

[Nandy]

Re: AC/Heater vents in 99 Blazer.

I took the glove compartment down and saw at least 2 actuators, I am convince that there are at least 2 more.

The actuators I saw are vacuum. I took the hose and felt the vacuum and could see the actuators going to their default.

One actuator is the one for the Max A/C which opens an inside vent to the air recirculates instead of just coming form the outside. The other actuator controls which duct/vent will blow the air. I could see it move depending in what setting I had it, floor, face, defrost. I would pretty much don't move with selections that blended different ducts, like if I moved it from defrost to defrost/floor I would not see that actuator move. If I went from face/floor to just face duct it would not move either. So I guess there is another actuator for that. Also, when I moved the thermostat control I could not see anything moving and I will think there is an actuator somewhere controlling a door in order to blend in the appropriate amount of cold and hot air.
I will take the ac controls out tomorrow if I have enough time. That way I can trace the cables/hoses.
Any other information will be appreciated.

Thanks!

 

[xtraham]

Re: AC/Heater vents in 99 Blazer.

I really cannot remember where the blend door actuator is on the 99 blazer, some are inside the HVAC plenum, try laying on the passenger floor and looking up behind the HVAC plenum (heater box) to see if you can find anymore actuators,

 

[Nandy]

Re: AC/Heater vents in 99 Blazer.

Dang, I am going to have to get that dash down. I cannot see anything else. I can tell the blender has to be electric as the control is electric unlike the vents control which is vacuum operated. the cables get together with other cables and get lost in the dash so I could not follow it. This is a full day work but I have to do it or I will be a Popsicles!

 

[LubeDude]

Re: AC/Heater vents in 99 Blazer.

I have a freind that works for a GM dealer and he told me that it is a factory screw up and there is nothing you can do about it. I actually had heard about this before. Now if it didn't do it at one time there could be a problem, but there will always be fresh air forced into the cabin.

 

[Nandy]

Re: AC/Heater vents in 99 Blazer.

I hear you LubeDude, but before if at least I could control the blender and have it been warm. I remember being able to do blend the heat/cold while now it is just cold as soon as I speed up. Anyway, if you see your friend maybe he can pinpoint where that heater/condenser blender is and I wont have to take the entire dash down. I had to deviate from the vent effort as the Blazer developed another problem that prevented me from using it but is now fixed so I will try the ac this coming sunday.
Thanks!

 

[Xcusme]

Re: AC/Heater vents in 99 Blazer.

I had basically the same problem with a 98' Venture. The flapper door to the outside air (on firewall) is controlled with electric motor. It's not variable, it's either open or closed to the fresh air. My problem was the door, even when closed, allowed air to sneak around the housing to firewall junction. I pulled the top of the dash and when the flapper door was closed, pulled the electric motor harness (3 conductor, if memory serves) and sealed the box to the firewall. This stopped the air intrusion. BTW, the easiest way , in my case, to access the fresh air flapper box was to lift the top of the dash.

The design problem with the Venture is the heater core is not sized for the cubic area of the cabin. I guess it's common practice to always have a positive cabin pressure (from outside air). The cabin air flows in through the flapper door and out vents at the cabin rear via one way vents to the outside. In defrost mode, the A/C compressor would come on and help dry the warm moist cabin air going past the a/c coils. So there was the problem, flapper open to help purge warm moist air, bringing in 20 below zero air, and expecting a small heater core to keep up.

Since I couldn't increase the output from the heater core, I pulled all interior panels, including roof panel and vents and insulated the van. I figured it 's a reciprocal thing, if you can't increase the heater core output, decrease the heat loss. It worked as I expected, more heat and a quieter ride to boot.

 

[xtraham]

Re: AC/Heater vents in 99 Blazer.

Open The Glove Box Door All The Way Down Till It Is Pointing At The Floor Now Remove The Vacuum Pod This Is The One That Changes The Air Flow Defrost /heat / Vent /at The Left Side Of The Door This Is Done By Pushing Up And Then Swing It Toward You Now Look On The Top Of The Heater Box Up High Near The Firewall You Can See The Blend Door Motor It Has 2 - 5.5 Mm Screws Holding It On The Heater Box This Is The Hard Part, All You Need To Do Is Remove 2 Screws Use A 1/4 In Drive Ratchet And A 5.5 Mm Short Socket A Thumbwheel Or Thumbwheel Ratchet May Also Work But It Can Be Done With A 1/4 Ratchet Have Fun Take Your Time Don't Get Mad It Will Come Out

 

[Nandy]

Re: AC/Heater vents in 99 Blazer.

Don't Get Mad It Will Come Out

Now you are getting tricky! LOL! I have been know to smoke out of my ears every know and then. But this is good info. I really appreciate it. Might take a peak at it tomorrow but will leave the hard work for sunday.

Thanks!

 

[Nandy]

Re: AC/Heater vents in 99 Blazer.

The blender for the heat/ac is electronic and I can see it rotating although that dont mean there is everything is tight inside of the blender compartment or the blender door itself. Also I found one actuator that is not working but I ran out ot time and could not take it out. However, that actuator dont seem to have an effect on the blending the air.
Anyway, I do need the diagram of the ac/heater system, with the vacuums hoses connections, actuators and ducts. I will make a new post "begging" for those. Otherwise it is going to be a long day..
Here is the post requesting the diagram:
http://forums.iboats.com/showthread.php?p=1890873#post1890873