Chewbacca hiding inside my AC vents?

Hey gang-
My 88 XJ has a new issue today. For a while now, whenever I turned the AC on (been using it a while now in SoCal so far this year), I got a long low GROOOOOAAAAANNNN (like chewbacca from star wars) from the vents. It lasted abuot 10-15 seconds, then would stop for the most part. During the whole thing, the air would blow out fine and it was cold and there was plenty of it.

So today I put the ac on high/max, and got....a bit cooler, but no air blew out from the vents. No matter what I slid the switch to: high/med/low or hot/cool or defrost, etc, I got no air. It DID get cooler in the cabin, as the air came out of the lower half of the vents that are used whenever I use the DEFROST setting. So I know the AC works, and it cools, it just ain't blowing out of the dash vents.

Any thoughts? Could it be something behind the dash? Or under the hood? I hope I won't have to yank that PITA dash panel off again, but I'll listen to anything at this point.

Thanks-

Mine did the same thing about a year ago, minus the visit from chewy. Later I had the radiator replace and it fixed it. I don't know why since they're only related via the heater. Good luck and I'd love to hear what others have to say.

I cant help you, but i had a similar thing this winter. My air would only blow out of certain vents. It use to make its mind up which vents would not work on any particular day. Try working your heater controls without the aircon and see if you get good flow. I never did tie down what was wrong but it would be interesting to know. I can only assume that youve got good vacuum if your getting cold air to your feet.
Mine kinda just fixed itself. It was really odd.

if you are only geting air though the defrost then you have a vac leak. the ac vents are controlled via the vaccume system and in the event of a vac leak the vents default to the defrost setting.

my fan wales like chewie as well when i first turn it on. after a while it quiets down. i got a feeling my fan motor is going out.

When in Defrost, the air should blow out the vents under the windshield. Are you getting air out other vents? Are they the same vents regardless of vent setting?

The vents are controlled by vacuum. If little to no vacuum is present, the doors default to defrost.

Mine "groan" a bit when I first start up. The vacuum builds and the doors actuate. You may have a vac leak. DO you have cruise control? If so, Does it work?

Re: Chewbacca hiding inside my AC vents?: update

Here's some much needed clarification:

Just went out and checked again. When the AC is on either max/normal/bi-level, I ONLY get cold air out of the top below-the-windshield defrost vents AND the lower half of the vertical slat vents furthest to the left and furthest to the right. (This lower half of the slat vents aims air ONLY at the small triangular vent windows, thus allowing you to see out of your sideview mirrors when you turn the setting to DEFROST. This lower half of only these outside slat vents is non-adjustable.)

I do not get air out of the adjustable vertical slat vents even though I have in the past.

When the slider is on DEFROST and cool and high, it still only pushes air at the windshield, like it's supposed to do on DEFROST, right?

To me, not knowing a damn thing about how the cold air is funneled to the cabin, in my mind I'm thinking that maybe whatever mechanism works to open doors, or slide vents, or somehow allow cold air to the cabin, instead of diverting it to the windshield (which may be the "fail"route when this part-piece fails), isn't doing it's job. So...it this a question of vacuum, like some have suggested? If so, where to start to look? Pull the dash? Under the hood? Inside the passenger front bumper @ the canister connections?

No idea. Thoughts?

Re: Chewbacca hiding inside my AC vents?: update

Saudade said:

...The vents are controlled by vacuum. If little to no vacuum is present, the doors default to defrost.

Mine "groan" a bit when I first start up. The vacuum builds and the doors actuate. You may have a vac leak. DO you have cruise control? If so, Does it work?

Click to expand...

wgregt said:

Here's some much needed clarification:

Just went out and checked again. When the AC is on either max/normal/bi-level, I ONLY get cold air out of the top below-the-windshield defrost vents AND the lower half of the vertical slat vents furthest to the left and furthest to the right. (This lower half of the slat vents aims air ONLY at the small triangular vent windows, thus allowing you to see out of your sideview mirrors when you turn the setting to DEFROST. This lower half of only these outside slat vents is non-adjustable.)

I do not get air out of the adjustable vertical slat vents even though I have in the past.

When the slider is on DEFROST and cool and high, it still only pushes air at the windshield, like it's supposed to do on DEFROST, right?

To me, not knowing a damn thing about how the cold air is funneled to the cabin, in my mind I'm thinking that maybe whatever mechanism works to open doors, or slide vents, or somehow allow cold air to the cabin, instead of diverting it to the windshield (which may be the "fail"route when this part-piece fails), isn't doing it's job. So...it this a question of vacuum, like some have suggested? If so, where to start to look? Pull the dash? Under the hood? Inside the passenger front bumper @ the canister connections?

No idea. Thoughts?

Click to expand...

ok greg. what you are describing is definitely a vaccume leak. the vent actuator is not recieving enough vac to keep the blend door on the setting you are trying to put it on. since it cant, its defaulting to the defrost setting which are the non adjustable vents on the top of the dash blowing on the windshield and the small vent on each side of the dash that blow onto the wing windows.

now that we know the cause, its time to find where its comming from. it can be from anywhere in the vac system- under the hood, the resevor bottle behind the front bumper, or behind the dash at the HVAC controls. i have dealt with this before. for me, many of the rubber grommets had deteriorated allowing for leaks. i would start at the vac bottle (the stock location is inside the pass side of the front bumper) and check the components. look for dry rotted, cracked or missing parts. depending on the size of the leak you may or may not be able to hear it with the engine running. i would say to check the system with the engine off first. fallow the vac lines and any branches. repair and replace as needed. a temperary repair can be done by covering the leak with electrical tape. it wont last long though due to the heat in the engine bay. the leak that i had was in the line about 6" back from the vac bottle. to remedy this i just relocated the vac bottle to inside the engine bay behind the battery. i ended up replacing a few more pieces due to dry rot. even one of the plastic lines had later developed a long crack in it.

with a little patience this is an easy fix

hth

do you need the vac bottle? cause ive been with out one for about 3 months, and the only thing i think i notice is my air pressure decreases through high acceleration.

Djmack said:

do you need the vac bottle? cause ive been with out one for about 3 months, and the only thing i think i notice is my air pressure decreases through high acceleration.

Click to expand...

hey! Same with me! I too have noticed that when the AC is on, and I'm on the gas, I either get hp OR I get AC, but I don't get both! And all this time I figured that's just the way it was. So you're telling me that if I'm hard on the gas, or I'm headed up a hill, with the AC on, that I SHOULD get 100% blowing cold AC if the vacuum lines are good to go with no leaks?

If that's the case, the heck...this thing has been on the way out for a while. I'll check the cruise control tomorrow am and report back (it too was working within the last week or so).

Let me ask this: do the vacuum canisters go bad and fail? I mean, are they like 'lectrics and either good/no good, or do they slowly fail mechanically?

Guess I'll start with the canister huh? Damn. I JUST had the front bumper off a bit ago too, installing a brush guard. Damn.

i value my vent settings and now my cruise control. for these two systems, it is best to keep the vac resevoir. in fact i had to re-relocate my vac bottle further into the engine bay (zip tied it to a somewhat unoccupied area to the rear of the ac compressor). when i installed the c/c servo. i pan on hitting the junkyard tomorrow and i will see if i can locate an acceptable replacement.

Yea, both the blower vents and the cruise control depends on vacumn. I had the vacumn bottle disconnected once. Running down flat roads I would have no problem, both would worked fine but with the slightest grade, the vents would de-fault to defrost and the cruise control would cease to function whch would require me to press the gas pedal to maintain speed thus putting more load on the engine which in turn would have even less vacumn. Large tires, high gear ratio and heavy load on the XJ do not help either.

The vacumn canister is just a storage device. With load on the engine, it produces less vacumn which then uses the stored vacumn until the load on the engine is reduced then the used vacumn is replenished. I ran my XJ many months without the canister with no ill effects 90% of the time.

update:
Drove it today, and the cruise control works just fine. So....does this mean the canister in the bumper must be good as well in order for the cruise to work fine? Should I pull the dash and start there to check for broken vacuum lines?

wgregt said:

update:
Drove it today, and the cruise control works just fine. So....does this mean the canister in the bumper must be good as well in order for the cruise to work fine? Should I pull the dash and start there to check for broken vacuum lines?

Click to expand...

yep. start with the hardest thing first:explosion. that way if its a simple fix under the hood you feel like an ass for not looking there first. but hey, what do i and most of those who contributed here know? i just type on the interweb thingymajig for the hell of it:compwork:. have fun and good luck!

So far, all vacuum lines and the canister check out as good. Saw this:http://www.alldata.com/techtips/Jeep/20020614b.html and wondered where the check valve is. Might be the problem? Anyone know where the check valve is, and what it looks like?

Mine sounds like a Loon (the Minnesota state bird).

I figure it's the blower motor about to die, but it only does it for a few seconds when you turn it on and it still blows air. It's been doing it for years, too. Heck, it adds charater- right?

i had a dead mouse in my squirrel cage that sounded (and smelled) horrible.

then it's nest embedded in my evaporator core, and my AC only works for a few minutes before freezing up. haven't taken the dash apart yet to fix.

ok, i wasnt even gonna suggest this as i cant see any connection what so ever only coincidences? Your man who replied to the first post had the same issue with mixed flow out the vents, he replaces radiator for unconnected matter, his flow from vents is restored? My flow was all messed up out the vents as was my heat, i checked vacuum all good, still i had crazy flow from DIFFERENT vents. I burped the system for unconnected matter, i get heat and full flow from all vents? Another guy who had same mixed flow problem as me (not the default defrost issue) gets his jeep on a steep incline as he tows someone out a ditch and he all of a sudden gets full flow? And his coolant bottle has dropped in level a few inches? Wtf? Gremlins responsible for all three?

Problem solved, though not by me!

Even though I traced every inch of vacuum line 2x, a had a friend do it for me as I watched, just to verify I was not nuts.

I watched as he found a small pencil-point-sized hole in the hard (brittle?) plastic vacuum line, right under the all-aluminum coolant overflow tank. It was facing the firewall, and even though I felt and looked along that line, I missed it.

He held his finger over it to check before we did a permanent fix, I jumped in the cab, ac on, and we were golden. We cut about .5 inch from the line, connected the two parts back with about an inch of wiper motor flexible rubber hose, and all is good. 100% full cold air at all times WFO from all vents, even headed up my steep 20% canyon road hard on the gas, on the gas in passing gear, with the cruise on...at all times. Works better than it has in years. I'm betting the hole was small, and has gradually gotten bigger, since I used to have 100% air, then only when I was off the pedal, then only on flat roads, then none at all.

Here's to simple and cheap fixes! Thanks for all of your input and help.

Till the next fiasco...

When it is cold out I have a colony of Wookies living in my steering column.