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AC Airflow Problems on 98TJ 4.0


 
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WingNut
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Joined: 14 Aug 2005
Location: Deer Park, Texas

PostPosted: Sun Aug 14, 2005 8:56 am    Post subject: AC Airflow Problems on 98TJ 4.0 Reply with quote

Fellow Jeepmiesters,

I have been experiencing a problem with me AC Airflow. When accelerating to enter the interstate the front vents will redirect the airflow to the defroster. When speed is stabilized to highway speeds the air will redirect to front vents, however I still have a partial flow to the defrost setting. In addition when at highway speeds, if I set the fan speed to high, I get a very loud howling sound, and I am unable to feel wither the air is predominately flowing from the floor, front or defrost zones. In other words it is as if the air zones are either equally split or totally blocked.

I have read the post on similar problems concerning the heated air and the yellow vacuum. Would this also concern AC Air? I do believe it is a vacuum problem. Can anyone help me narrow the problem down to a specific target area.
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KnightFire
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Joined: 07 Jan 2004
Location: Hanover, MD

PostPosted: Mon Aug 15, 2005 2:08 pm    Post subject: Reply with quote

Just for S&Gs check the vacuum line on the intake of the motor, make sure it's fully seated and doesn't have any cracks in the tubing.

I recently had mine come off for no reason, I was only getting air from the defroster vents, got it home, popped the hood, sure enough the vacuum line had backed off. Put it back on, good as new.

KnightFire
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2002 TJ Wrangler X
Patriot Blue 4.0L
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WingNut
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Joined: 14 Aug 2005
Location: Deer Park, Texas

PostPosted: Mon Aug 15, 2005 8:24 pm    Post subject: S&G Remedy Reply with quote

OK, i physically checked the Vacuum Lines, and sure enough there was a fitting that backed off.

However, I have a single line that runs from the intake maifold across the firewall to a tee from there one side punches thru with the ac tubes and the other,, well that is the problem it was hanging lose under the battery with a split boot.

it is 1100 at night here and with a flash light i am unable to locate a spot where it originally hooked too. I can see what looks like the blower moter fan casing, but with the battery and limited lighting i did not see a vacuum hookup point.

i also noticed that it would reach the area of the distributer, thinking it had some sort of vacuum advance,,, but i may be wrong in that assumption provided the ECM controls that,, Doesnt it???

I would like to thank you for helping me, perhaps tomorrow i can pick up a manual with a detailed vacuum drawing.

Joe
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WingNut
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Joined: 14 Aug 2005
Location: Deer Park, Texas

PostPosted: Tue Aug 16, 2005 7:19 am    Post subject: Udate: Problem Sovled to 50% Reply with quote

I did find the leak. Could not find the point to which the loose Vacuum line attached.

Temporary solution was to bend the boot back to seal leak. This worked wonders as I froze myself on the way to work. There were no fluctuations in vent air.

It even feels as if the acceleration is better and at hwy speeds the RPM's were 200 lower at 65mph. This also seemed to fix the delayed starting issue too. Thru all my online research, I noticed that this was also due to possible vacuum leak.

Now it is just a matter of finding the schematic. However, this leads to another question. Which Service manual comes with the better pictures? I have seen posts that say both the Haynes and Chiltonís did not offer much in their diagrams to help troubleshoot the actual locations.
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KnightFire
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Joined: 07 Jan 2004
Location: Hanover, MD

PostPosted: Tue Aug 16, 2005 9:58 am    Post subject: Reply with quote

Glad you found it!

I would look on line for a FSM (Factory Service Manual) these are the most complete books, the others you mentioned are great and I use them often, but I honestly think the FSM is the best all around book, especially when dealing with those odd items such as vacuum lines and such.

Good Luck

KnightFire
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2002 TJ Wrangler X
Patriot Blue 4.0L
Check Website for Mods/Photos

Amsoil Dealer
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