A/C swaps to defrost vents when at speed

Jaxon B.

Jaxon B.

TJ Enthusiast
Joined
Aug 11, 2020
Messages
170
Location
West Palm Beach, Florida
I have a 98 TJ, whenever I drive at the range of 45-70 mph, the AC will switch to the defrost vents and stay there for a while, before heading back. The only other time this happens is when I first start it up, and the AC starts making a high pitched noise through the defrosts and I have to turn the fan speed low for a second and then back on high for it to blow out of the proper vents. Is this an issue with the vacuum lines? or something else I don't know?
 
It's a vacuum hose leak. Mine always crack where it goes into the firewall or where it connects near the manifold.
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I second the vacuum leak in the system. I had a similar issue where it would change vent locations if i was accelerating up long grades in the mountains. High load is low vacuum. Mine was resolved with replacing a leaking one way valve located on the engine firewall. Its shown in Boogieman's picture above. Check the operation of those while looking over your lines.
 
Juggernaut said:
I second the vacuum leak in the system. I had a similar issue where it would change vent locations if i was accelerating up long grades in the mountains. High load is low vacuum. Mine was resolved with replacing a leaking one way valve located on the engine firewall. Its shown in Boogieman's picture above. Check the operation of those while looking over your lines.
Click to expand...
Exactly what happens with mine, I live in Florida so I have no mountains but we do have the tall highway ramps, and that particularly is where the vents switch, I'll check my vacuum hoses near the firewall and update!
 
After days of trying to find it, I have found the most apparent and visible crack I have ever seen in a hose. Anybody know where to find a replacement for this hose?

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You can just take a short piece of snug fitting rubber hose and use it as a repair coupling, otherwise a generic tube is usually available at most auto parts stores in the help section.
 
I went to AutoZone and bought 3 feet of generic vacuum line for 5 dollars. I cut the existing tube right where it was broken and slipped the replacement into the old tube (the portion that was not rotted away) and slipped heat shrink over it. That sealed it up really good, and I did the same to the t-cross portion, saving the connector and putting the replacement line into the connector, and sealing it with heat shrink. Fixed it up and now the A/C vents work properly! Thanks to everyone :)

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Yes I tucked away the cables after I took the picture
 
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