HVAC issue - air only coming out of dash

[The Warden]

Hello!

I've had an issue crop up. I first noticed this near the end of last winter, but didn't mess with it due to a lack of time and due to it not really being a problem with summer coming up. But, now it's winter and it'd probably be a good idea to take care of it.

My truck has factory air conditioning. Regardless of where I put the selector lever, I am only getting air out of the in-dash registers. I can't get air out of the defroster vents or out of the floor ducts. Everything else seems to be working fine (a/c compressor comes on when it's supposed to, "fresh air" door opens and closes as it should, lever feels the same, etc), and IIRC the system would default to defroster mode if there was a vacuum problem. So, it sounds like it has to be mechanical in nature.

I should note, however, that switching the lever to "Floor" or "Defrost" DOES make a difference. While I still won't get any air blowing out of the floor ducts or the defroster vents, the amount of air coming out of the in-dash registers DOES decrease.

I'm going to take apart the center dash area tomorrow (while doing other things to get my truck ready to drive to L.A. on Thursday); maybe I'll just get lucky and there'll be something in there keeping the door lever from moving. But, if not, any ideas on what it might be?

IIRC some people have had a problem with the plastic breaking and making one of these doors inoperative; don't know which door, though, and I don't know what the symptoms are.

Any thoughts? Thanks!

 

[Dsl_Dog_Treat]

Tim,
Pull the radio out first and operate the controls, the one right directly behind the radio is the PITA one to get to. You should be able to see the modules operating with the truck running.

From what you're describing, it sounds like that one may be the culprit.

Could be the vacuum module is hanging up and remaining closed.
IIRC, the default mode for that one will be extended to push air to the dash and retracted will force the air flow lower.

Goldies issue was a broke arm on the module behind the radio keeping the diffuser door open forcing the air to the dash only.

The second module swithches air flow from the dash to floor.
Good luck as the module replacement will prolly recquire some dash disassembly.
Hope this helps some.

Good luck.

 

[gonecamping]

I had a similar issue with my truck except the air came out of the defrost vents. The dealership replaced my vacuum box.

 

[Diezel_Cowboy]

SmokinStroker's truck had the same problem.......the vac. valve behind the radio was working, BUT the chincy linkage was bending since the valve arm itself was rusted solid. When we tried to force the flapper in the air box the plastic valve just snapped now he just uses a piece of foam in the floor opening to send more air to defrost. I expect you are not looking for this type of poor man's fix but I also suspect that the valve pivot rod is rusted solid and not turning even though your vac valve is still operating correctlly. This is possible because the braket that the vac valve is on is not solid so it lets the valve go through the motion without doing its job.

 

[The Warden]

Well, there went the easy answer...



Okay, started tearing apart parts of the dash. I checked the vacuum pot behind the radio first; worked just like it's supposed to. It opened partway when I selected "Mix" and opened all the way when I selected "Defrost".

I then went and found the pot below and to the right of it (the one that controls the "dash register" flap). I then selected "Vent", and the vacuum pever moved perfectly.

It looked like I might be able to access the door from the heater core cover, so I went and removed it. And, sure enough, I was able to see and feel the door. And, that's where I found the problem.

No rust in the system all the connectors are loose and free-moving. Problem is, the arm coming from the vacuum pot is the only thing holding the flap in place. The flap is completely loose otherwise; if I could figure out how to disconnect the vacuum pot arm, I could remove the flap completely. I've never looked in there, but either the hinges broke, or the plastic (on the flap or the unit?) broke.

I presume there's no way to repair this? Is the unit available new, or do I get to go junkyard diving? How much of the dash has to come apart to get this thing out? I imagine there's no way I'm going to get this fixed in the next 6 hours...



Thanks!

{added on edit} Can the vacuum pot arm be disconnected from the flap without removing the box? I'm thinking on the lines of pulling the box as a temporary measure until I get back from L.A. and/or can figure out how to fix this once and for all...I'll still get air out of the dash vents, but at least I can get SOME air to the defroster, right?

A fairly speedy answer would be greatly appreciated; I have a LOT to do before losing daylight...

Thanks again

 

[wrsainio]

I had the same problem a couple of years ago on an 86 xlt. I bought that door c/w new hinge from ford. Doubt a wreckers one would last very long and it is way too much work to replace. sounds like your dash is pretty well all apart so it shold not be much more trouble installing. I had mine all apart by the time i figured out the problem. Wilf.

 

[The Warden]

The flap can be replaced by itself?!? SWEET!!

BTW, I just finished removing the old one...with the box in place; my hand BARELY fits in the opening...would need to put ice on it, except it's cold enough outside that ice isn't necessary

I didn't realize how cheap of a design the hinge was...I thought it was a metal bar like some other setups. I didn't remove the section of the hinge that's attached to the box, so, how does the hinge attach to the box?

Nice to know that Ford still sells the bloody thing...I even have a part number on the flap I think I get to run without the flap until I get back from L.A., though...I have to spend all day tomorrow packing the truck/trailer, and then leaving here at 0500 on Thursday

Do you by chance remember what Ford charged you for the flap? I presume the box has to come out and apart in order to replace it...

Thanks again!!

 

[towcat]

tim-
the blue CC has a intact setup. If you pull it apart gently, you can have it. If you want me to do it, it will cost. I'm down with the flu right now, so it is prolly faster if you came by and got it.

 

[Agnem]

Hope you feel better Calvin. The warm December we are having around here has given everyone in my family a nill chance of being completely healthy for Christmas.