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Unread 07-24-2007, 08:49 PM   #1
qbert213
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1997 TJ Wrangler 
 
Join Date: Sep 2006
Location: Baton Rouge
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Air Conditioning Duct Issues

I have a 97 Wrangler Sport that blows cold air... but only out of the defrost vents. When I choose the setting to blow out of the front vents, it makes a terrible chattering sound and nothing happens. When switched back to defrost it goes back to normal. This has been an issue for several years with no luck from various shops. Someone recommended the dealer but Im not sure Im ready to overpay for a easy fix (if thats the case). Any ideas from the experts?

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Unread 07-24-2007, 08:51 PM   #2
Rocky529
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You have a vacuum leak in your engine compartment.
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Unread 07-24-2007, 09:49 PM   #3
braddock
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You are going to have to do some exploring. Open the glove compartment and take it out. In the upper left hand area of the firewall you are going to see a plastic coupling with little red, green, yellow, black, and blue tubes.



This is the vacuum supply to the HVAC. Disconnect this coupling and crank your engine. Feel the firewall side of the coupling for a vacuum. If you feel the pull of the vacuum your problem is probably not on the engine side of the firewall. The other section of vacuum hoses runs past the center column and into three mechanical actuators for the different HVAC settings. The actuators are just to the driver's side on the very bottom of the center column near the center console. If you have had a few beers it won't be any problem to grab your center roll bar, swing around it like a monkey, and put your head under the steering wheel to see this:



You'll see the vacuum lines running to the actuators. If you don't want to pass out from the blood running to your head, removing the drivers seat helps. My problem was that one of the actuator arms actually broke off. It made a sound much like the one you described when I switched settings. The red line is the front panel actuator and you can see mine hanging there limp after I took the actuator off its mount so I could work. I used an old screw to thread the actuator back on and all good from there. Iíll help if I can.

Here is the little actuator bastard that kept two previous owners from having AC and took a grand off the price I paid for my girl:

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Unread 07-24-2007, 09:59 PM   #4
qbert213
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Thanks for the help! Pictures make things so much easier. I will try and see if I can find the problem this weekend and keep up the post. Thanks again!
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Unread 07-24-2007, 10:08 PM   #5
mike06X
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great pics and info - i need one of those little arms for mine - i have a bent screw jammed in there and a tie strap holding the screw over so i get a/c when i need it; buti need to fix it, because nothing else works now unless i give it the reach around.
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Unread 07-24-2007, 10:53 PM   #6
stogie25
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The poking around is a great suggestion. Here is a write-up of my fix.

Good luck,

I hope this helps anyone whose vents and or heat doesn't blow, or anyone whose vents stop working when entering the highway or going up a steep hill.

I am the original owner of a 1997 TJ. I (also known as the loose nut on the steering wheel) am one of the few original pieces left on my Jeep. Recently I have discovered several other pieces of original equipment, all of which control the direction of air from my vents and heater. My tale starts about five years ago when my dashboard vents stopped blowing. My under dash heater and defroster still worked, so I just blew the problem off. This year my under dash heater stopped working, leaving me with only the defroster. Something had to be done.

I started at the control switch. I found the vacuum lines attached to the back of it, and blew them out with a football needle and my garage air compressor. I also found a splice in the line behind the glove box. I cleaned that out as well. I insured that everything was correctly seated and tried the vents and heater. No dice.

Undeterred, I started poking around under the dash. I discovered three vacuum activated switches with arms attached that control the air direction. They did not budge when the control was set to either vent or heat, and the input to them showed vacuum on the gauge. I was able to manually move them, thereby changing the direction of the air. I knew I was close. I contorted myself into a two hundred and fifty pound pretzel, and changed them out. This took about an hour, and cost about a hundred dollars. To my great disdain, there was still no air blowing through the vents or under dash heater. The switches at least tried to move (a definite improvement) but it seemed the vacuum was not quite strong enough to move the arms.

I crawled back under the dash and traced all the vacuum lines, identifying the black one as the source vacuum. It penetrated the firewall on the passenger side, not far from the battery. It went to a three way junction. One of the lines from the junction went predictably to the intake manifold near the rear of the drivers side. The other line went under the battery where it was broken. I sealed it up with a nail. Upon checking, I had full control of my air direction.

This did not feel like a complete repair with a nail plugging up a mystery vacuum line, so I perused a used car lot nearby and found another 97 Wrangler. I crawled under and traced the line to a vacuum reserve container near the bottom of the Jeep. My next stop was the auto parts store for a few feet of vacuum line. The problem seemed to be fixed.

That night I went to pick up a friend to take to the bar, and when entering the highway my vents stopped working and defaulted back to the defroster. As soon as I let off the gas a little it went back to vents. I remembered the Jeep doing this many years ago when the vents worked, and remembered that it was annoying then. Now I was emotionally involved with this repair and had no intention of letting this annoyance continue. I searched the internet, and learned that I was not the only person with this problem. I could not find anyone who had posted a solution. The internet was of some help, as it directed me to a Jeep TSB that told of a one directional vacuum valve in line with the feed, but did not give a part number. I called a friend at Jeep, who informed me that he had the same problem. He hoped I was successful at finding a solution for both of us. He diligently kept working on his part the solution until he found a part number from the Cherokee, which we figured would work. Due to the remote location of my friend at Jeep, I had to stop by a local dealership to pick up the part. It cost about seven dollars. While at the dealership, I told the parts people about my problem, and asked if they had ever heard of similar problems, and they told me that the Grand Cherokee has a small reserve reservoir in line with the vacuum source supplementing the larger reserve container. For another eleven dollars I figured I would try that as well.

I got home, replaced the valve, which was a slightly different part, and installed the in line reservoir, which plugged directly into the valve. I test drove the Jeep several times on the highway, and was unable to make it fail. I was also able to turn off the motor with the key in the accessory position, and keep the vents blowing, something I donít ever remember the Jeep doing before. It is supposed to snow tomorrow morning, and I look forward to having the heat blow at me for the first time in years.

Check valve 4549209 $6.54
In line reservoir 4677204 $11.06a
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Unread 07-24-2007, 11:35 PM   #7
braddock
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You know, my vacuum reservoir hose popped off a few months after my AC fix and the air defaulted back to defrost. I crimped off the hose to the reservoir with a Ziptie and forgot about it till you just mentioned it. I have noticed no performance problems without the vacuum reservoir and the air works perfectly. It's like this is the Jeep's appendix. If you have one great...if it's clipped off doesn't matter so much.
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Unread 07-25-2007, 07:25 PM   #8
TJW909
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wow thanks for all the info. I worked on mine this weekend and found a vac. line under the battery box with an a aluminum plug stuck in the one end looked factroy it was just laying there. It comes off a 3 way tee. You have the supply from eng on one end, one end going thru the firewall for supply for doors and then the 3rd end had this plug does this sound like any thing you seen on yours or the one you looked at? Where did this check and resv. go that you installed? Thanks for any input this vent thing is driving me nuts.
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Unread 07-25-2007, 08:20 PM   #9
braddock
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The vacuum reservoir is already on your Jeep. It is a located under your battery tray. That line with the aluminum plug is supposed to run to it. Someone probably put that plug there to stop the vacuum pressure leaking. Try Crimping that third line with the plug closer to the 3 way tee and then check your AC. You are losing vacuum pressure somewhere. If you aren't losing any pressure in the engine compartment you'll need to check the spots I mentioned above.
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Unread 08-25-2007, 02:52 PM   #10
qbert213
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After inspecting the vac lines and not finding any leaks I was able to find out that is was one of the plastic acuators. The leg of the acuator was broken at the arm so it needs to be completely replaced. Any clue where to pick one of these up at?
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Unread 08-25-2007, 03:59 PM   #11
nolo263
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Quote:
Originally Posted by stogie25
The poking around is a great suggestion. Here is a write-up of my fix.

Good luck,

I hope this helps anyone whose vents and or heat doesn't blow, or anyone whose vents stop working when entering the highway or going up a steep hill.

I am the original owner of a 1997 TJ. I (also known as the loose nut on the steering wheel) am one of the few original pieces left on my Jeep. Recently I have discovered several other pieces of original equipment, all of which control the direction of air from my vents and heater. My tale starts about five years ago when my dashboard vents stopped blowing. My under dash heater and defroster still worked, so I just blew the problem off. This year my under dash heater stopped working, leaving me with only the defroster. Something had to be done.

I started at the control switch. I found the vacuum lines attached to the back of it, and blew them out with a football needle and my garage air compressor. I also found a splice in the line behind the glove box. I cleaned that out as well. I insured that everything was correctly seated and tried the vents and heater. No dice.

Undeterred, I started poking around under the dash. I discovered three vacuum activated switches with arms attached that control the air direction. They did not budge when the control was set to either vent or heat, and the input to them showed vacuum on the gauge. I was able to manually move them, thereby changing the direction of the air. I knew I was close. I contorted myself into a two hundred and fifty pound pretzel, and changed them out. This took about an hour, and cost about a hundred dollars. To my great disdain, there was still no air blowing through the vents or under dash heater. The switches at least tried to move (a definite improvement) but it seemed the vacuum was not quite strong enough to move the arms.

I crawled back under the dash and traced all the vacuum lines, identifying the black one as the source vacuum. It penetrated the firewall on the passenger side, not far from the battery. It went to a three way junction. One of the lines from the junction went predictably to the intake manifold near the rear of the drivers side. The other line went under the battery where it was broken. I sealed it up with a nail. Upon checking, I had full control of my air direction.

This did not feel like a complete repair with a nail plugging up a mystery vacuum line, so I perused a used car lot nearby and found another 97 Wrangler. I crawled under and traced the line to a vacuum reserve container near the bottom of the Jeep. My next stop was the auto parts store for a few feet of vacuum line. The problem seemed to be fixed.

That night I went to pick up a friend to take to the bar, and when entering the highway my vents stopped working and defaulted back to the defroster. As soon as I let off the gas a little it went back to vents. I remembered the Jeep doing this many years ago when the vents worked, and remembered that it was annoying then. Now I was emotionally involved with this repair and had no intention of letting this annoyance continue. I searched the internet, and learned that I was not the only person with this problem. I could not find anyone who had posted a solution. The internet was of some help, as it directed me to a Jeep TSB that told of a one directional vacuum valve in line with the feed, but did not give a part number. I called a friend at Jeep, who informed me that he had the same problem. He hoped I was successful at finding a solution for both of us. He diligently kept working on his part the solution until he found a part number from the Cherokee, which we figured would work. Due to the remote location of my friend at Jeep, I had to stop by a local dealership to pick up the part. It cost about seven dollars. While at the dealership, I told the parts people about my problem, and asked if they had ever heard of similar problems, and they told me that the Grand Cherokee has a small reserve reservoir in line with the vacuum source supplementing the larger reserve container. For another eleven dollars I figured I would try that as well.

I got home, replaced the valve, which was a slightly different part, and installed the in line reservoir, which plugged directly into the valve. I test drove the Jeep several times on the highway, and was unable to make it fail. I was also able to turn off the motor with the key in the accessory position, and keep the vents blowing, something I donít ever remember the Jeep doing before. It is supposed to snow tomorrow morning, and I look forward to having the heat blow at me for the first time in years.

Check valve 4549209 $6.54
In line reservoir 4677204 $11.06a

Post some pics where this part goes brother..
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Unread 10-24-2007, 12:49 PM   #12
AlexTJ
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Join Date: Mar 2006
Location: Kansas
Posts: 498
When I try and turn my vents on, whether on hot or cold, no air comes from anywhere and I hear this horrible whistling sound.

My heat hasn't worked at it's best for awhile either, I think the door may not be properly switching.

So will the above solutions probably fix my issues?

P.S. Just in case it's important: My airconditioning hasn't worked for awhile because of a coolent leak
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