After a buddy of mine recharged my AC (Not a professional, but has done it before), my AC (which is nice and cold now) swaps to Defrost when I, for example, go onto a freeway onramp or speed around a grandma. I notice it hits defrost at 2k rpm.

Any input would be great. I plan to check my vacuum canister when I stick on my front tow hooks.

 

The selector is actuated by vacuum from the engine. You turn the **** and a vacuum line either uses the vacuum or absence of vacuum to select the desired setting. Of course you don't want positive pressure going to the engine so there is a check valve in that line. This allows air to only flow one way. That check valve has a tendency to not work after a while. If you like your head way under the passenger side dash and look towards the center, you will see that hose that holds the check valve. Mine has been doing this for years.

Two options, deal with it and learn to feather the throttle as much as possible. Or try to change out the line. They should be cheap, but I see no easy way of reaching up there and removing and replacing.

I deal with it. It's just a comfort setting, and I like fresh air so Windows are always down.


It has nothing to do with the AC system working. It has everything to do with that vacuum line

Nick

 

when i first purchased my jeep, the ac only ran on defrost. after checking online forms and under the hood, the line that goes into the throttle body was just laying there unplugged. i figured it had to do something with vacuum, so thank you, i'll look into it since it really bothers me. I'm an AC sorta person who likes it cold.

 

My apologies, I just realized you have a 98. The information I have you is based off of a 99+. It could be the same setup, but due to my illiteracy, I possibly gave you false information.

I just googled your concern and came up with this. Hope it helps.

http://www.jeepforum.com/forum/f13/m...1221123?page=1

 

that makes sense since i couldn't find it on my vacuum diagram.

i found another forum post that hit my problem right on it's head

http://www.jeepsunlimited.com/forums...um-check-valve