Vents Won't Work

[drase]

My A/C and Vent mode will only work in Defrost mode. No air will blow out of vents on dash that blow towards the driver & passenger. Anyone got an idea what the problem is?

[54bobby]

I think if I remember correctly, there is a vacume line that connects to a bladder under the front bumper. check the lines. some of the more knowledgeable guys will chime in shortly I'm sure. 

[92tanMJ]

Yep there is a vacume ball in the fornt bumper. I would check that first, is they become damaged pretty easiley.

 

Does it blow out of the vents in heat mode?

 

If not I would check the vacume lines, the mechanical flapper, and check to make sure the hoses are still hooked up the the dash vents.

[drase]

Not sure about in heat mode, its still hot in FL so haven't tried it, but will now.

[cruiser54]

On the passenger side firewall is a black tube traveling down behind the battery and into the back side of the passenger side front bumper. That hose gets cracked, eaten by battery acid etc. I generally move the "ball" from the bumper up into the engine bay not far from where the black line enters the firewall. On Renix Jeeps, mounting it to the bottom side of the metal plate which holds the coolant bottle works very well. 

[92tanMJ]

Not sure about in heat mode, its still hot in FL so haven't tried it, but will now.

 

If it doesnt blow out in the vents in heat mode as well then it's most likely a vacume issue or the flappers stuck on defrost

[HOrnbrod]

On the passenger side firewall is a black tube traveling down behind the battery and into the back side of the passenger side front bumper. That hose gets cracked, eaten by battery acid etc. I generally move the "ball" from the bumper up into the engine bay not far from where the black line enters the firewall. On Renix Jeeps, mounting it to the bottom side of the metal plate which holds the coolant bottle works very well. 

 

Here's one way to do it. Just make sure you keep the vacuum check valves in-lined properly. :

 

http://comancheclub.com/topic/16154-vacuum-reservoir-relocation/?hl=caveman

[cruiser54]

Nice underhood light switch. Kinda "retro"......

[HOrnbrod]

Nice underhood light switch. Kinda "retro"......

 

:yes:   Yeah, the original mercury switch drove me crazy. Wish now I had done it in black though......

[cruiser54]

I know the feeling. I leave it unplugged for the most part. 

[Zebvance]

I have this problem too. The PO removed the "Ball" for some reason. Not trying to hi jack but does anybody know where I can get another?

 

Ps. Mine is a factory non ac model

[cruiser54]

I have this problem too. The PO removed the "Ball" for some reason. Not trying to hi jack but does anybody know where I can get another?

 

Ps. Mine is a factory non ac model

No cruise? Look under the hood of most any Ford or Chevy and you'll see them. Mine looks like a big soup can and came off a Ford. 

[Zebvance]

 

I have this problem too. The PO removed the "Ball" for some reason. Not trying to hi jack but does anybody know where I can get another?

 

Ps. Mine is a factory non ac model

No cruise? Look under the hood of most any Ford or Chevy and you'll see them. Mine looks like a big soup can and came off a Ford. 

 

No cruise from the factory either. do you know what the actual name is. I will order it off ebay now if I could find it.

[88whitemanche]

Vacuum canister

[Zebvance]

does any body have a vacuum schematic that shows it. It would prolly help me and the OP.

[Guest]

Another thing of note I discovered upon taking apart the dash in my 87. There is a small Y shaped inlet tube where 3 lines meet; it's about 5 or 6 inches back from where the HVAC controls are located (headed towards the passenger side). Not sure if it's the same for later models, but sometimes the Y connector can disengage itself from one of the lines, hence, defrost only mode.

 

I chased vacuum lines all over my truck like the others said, only to finally discover they weren't the problem. Took long enough, and now I have working air again. If you can't find a leak in your system, this may be the problem...  :smart:

[92tanMJ]

I have this problem too. The PO removed the "Ball" for some reason. Not trying to hi jack but does anybody know where I can get another?

 

Ps. Mine is a factory non ac model

 

Junk yard would probably have a couple cheap if theyres one close to you. Or someone parting out an MJ or XJ. Pretty sure the one in my 92 and 98 are the same...

 

 Red Rocker79, on 18 Mar 2014 - 5:32 PM, said:

 

    Another thing of note I discovered upon taking apart the dash in my 87. There is a small Y shaped inlet tube where 3 lines meet; it's about 5 or 6 inches back from where the HVAC controls are located (headed towards the passenger side). Not sure if it's the same for later models, but sometimes the Y connector can disengage itself from one of the lines, hence, defrost only mode.

    I chased vacuum lines all over my truck like the others said, only to finally discover they weren't the problem. Took long enough, and now I have working air again. If you can't find a leak in your system, this may be the problem...  [ :smart:]

 

On the later models it's behind the glove box but same issue

[carnuck]

Also see if the vacuum hose is off the vacuum motor right above the gas pedal.

 

A new vacuum ball is about $17 at Napa. Here's mine mounted under the hood (my bumper is extended forward for a hideaway winch)

 

[1989 Eliminator]

Yup if you move the vaccum canister under the coolant bottle, you can use some of the old lines (if they are good) to hook everything back up normal. This will eliminate a TON of vaccum line which in return gives less of a change of a leak. I can send pictures if wanted.

[drase]

A vacuum line was broke. Replaced it and blows cool air through all vents!

[cruiser54]

A vacuum line was broke. Replaced it and blows cool air through all vents!

Gotta love it!! Congrats.

[floridaftwman]

I had this problem, and thanks to the forum I was able to isolate it. My canister has two tubes. I inspected and replaced one labeled "vac" that routes to the three way connector.  The second hose was severed near its connection going through the firewall. I taped it up and got it to work, restoring function of the vents. However, I don't reckon this is gonna last. What are thoughts on using heat shrink tubing for a more secure repair? Best bet on getting a replacement?? can't find what this part is called for the life of me.