HVAC comes out of defroster vents only

[downzero]

I assume a vacuum issue. Anyone know these systems and have some advice? No matter what I set it at.....it comes out of the defroster vents. My AC is cold, my heat is hot as hell......i just have no control over where it comes out. Vacuum? Switch? If anyone has a schematic, advice, or whatever, I'm all ears. I've done some poking around but all the vacuum lines appear hooked up under the dash but I don't know what the deal is.

 

[Quartermile]

The selector switch for AC Max AC floor etc is vacuum operated on most vehicles. might have a leak

 

[snomaker321]

passanger side there is a vaccuum line going font this ball thingy into the cab. It most likely came in contact with the exhaust and melted in half. Look around that area for a broken line. Im sure someone else willl have a better description but i had the same problem on mine and that was it

 

[8sechonda]

i was just bout to post bout this prob. mine is doing the same crap.. except when it wants too it will change from defrost to vent.. all by its self.. they dont make rangers like they used too

 

[snoman6115]

check your vaccum lines in the engine compartment. especially if u have auto hubs. if one is shot it will leak there and mess up ur heat control. had that happen to me put manuals in and connected the vaccum lines different untill everything worked. i ahd a guy who knew what he was doin so ide say find a really nice detailed vaccum diagram not jsut the one under the hood

 

[snomaker321]

also, use the search feature. i know for a fact that there are at least a few other threads out there that will help you

 

[hondaxr650]

Most likely a broken plastic vacuum line under the hood somewhere. They default to defrost when vacuum is lost.

 

[subydrift]

I have the same problem. Can you just tear out the hard vacuum lines and use the regular rubber ones?

 

[downzero]

One thing I did change this year is to a set of manual hubs. Where's the easiest place to plug off the vacuum line to the hubs themselves? Perhaps I caused the problem myself.

 

[downzero]

I found the problem. The vacuum ball, which is between the inner fender and the front fender, was broken in half. This caused a large vacuum leak which of course contributed to a rough idle and the fact that my AC didn't work.

I tried gluing it back together, but it still leaked. So, my solution? I removed it completely and hooked the vacuum lines together. No more vacuum ball, no more leak, and my A/C works great.

For future people who are trying to search this, there is one vacuum line near the A/C evaporator box that feeds both the 4wd hubs and the vacuum-operated A/C stuff. It goes into that "ball" which stores vacuum for when you mash the gas or other situations where there is no vacuum available.

The way this ball works, it has two bolts in it below the airbox and if they flex just right, the ball will crack and leak.

You will need to remove the air filter box (pull it really hard. It won't break, trust me!). and unbolt a bunch of rusty crap to get to this thing. You'll also want to remove the washer fluid/antifreeze tank.

 

[maemae]

I have a 2wd ranger that is having the same problem. Is there a way to find the leak. This whole vacuum line thing is a mystery to me. Technical diagrams would be a great help.

 

[wickland111]

My 2002 explorer sport is doing the same thing. I checked the lines going to the ball vacuum canister under my passenger fender, checked the lines, and checked the vacuum motor behind my glove box.

When I tested the vacuum canister, It acted like a gate valve. One end allows you to create vacuum, where the other wont hold a vacuum at all. Is this correct?

The lines, is simply tested to see if the held vacuum. They seem fine. Im not really sure which one should hold vacuum and which shouldn't.

I used a vacuum tester kit for all my testing while the vehicle is running and ac is on. When I checked the line that goes on the vacuum motor behind my glove box, the line that goes into the motor was only at 2 lbs when on max ac. Is that enough? When i hook up my vacuum pump and draw about 10 lbs on it ,the motor seems to work fine. Even then though the air doesn't come out of the vents.

Any help would me much appreciated. I am a broke a#$ law student.

Broc

 

[adsm08]

Your does not sound like correct operation Wickland. It should be a two position vacuum motor. The upper nipple pulls it half way down, the the lower one pulls it the whole way down.

You should have the vent/floor position though.

 

[wickland111]

No, you are talking about the vacuum motor that switches between the floor and the dash. There are 3 vacuum motors in my explorer. The one behind the glove box controls the circulation of air in the cab or outside the cab(Max AC vs. AC). The one behind the dash and above the one you were talking about controls switching between the defroster and dash vents.

When I hook up to both the circulation motor and the motor that switches between the defroster and dash vents, I notice that they work perfectly when I apply at least 4 lbs of vacuum. I checked the lines leading to them and they both only supply 2 lbs vacuum. Is that sufficient?

Im not sure where to check now. I assume where the vacuum goes into the cab.

I also already tested the vacuum canister and the lines to and from it.

Any Suggestions?

 

[wickland111]

First, let me correct myself as vacuum is measured in inches, not lbs.

Also, I wanted to let you know I fixed the problem today. It was a vacuum line with a pin hole.

After thinking more about it last night, I decided to start at the vacuum tree and move towards the firewall. I checked the redline that goes from the vacuum tree to the vacuum canister. I checked each break of line and connector. It was simply one of these pieces of line. It had a pin hole where it looks like it was rubbing against something in the engine compartment.

I feel dumb as I should have done that first. Those lines should supply roughly 15 inches of vacuum, fyi. Im not sure what it would measure after the canister, I never measured after it as I fixed my problem. But all the way to the canister it should be roughly 15 inches of vacuum when the air is on max ac and at idle.

I hope this helps someone.