xdescrubx

When I am on the highway, no matter what setting, my AC switches itself to defrost. It happens more when the engine is under load, like going uphill or towing the boat. When I let off the gas it immediately goes back to whatever setting it is set to, which is usually MAX. City driving I have no issues, under 55ish MPH. If I floor it at lower speeds it works fine, at highway speeds it will switch. Its a 1995 Cherokee country 4.0, no engine mods except a free flowing exhaust. I have replaced the resistor recently. And had a mechanic evacuated the system when I installed a new compressor. It has always done this since I have owned it. Thanks for the help.

xdescrubx

Oh I also have the aw4 tranny.....

FL Denmark

the controls are operated on vacum, thats why the different ways of driving will affect it. but it will only affect it if the vacumball, located right behind the frontbumper in the passengerside is either cracked or disconnected.
its a vacumresiovor that will help even out the different vacum in the manifokd, related to different throttlepositions / engime rpms

the default setting for your blower is defrost, which is were it will go without vacum.

so, check the vacumball and the tube to it fir cracks and disconnects

good luck with it

xdescrubx

Awesome there is w little crack in the line. One more thing my cruise is disconnected electrically, mechanicly still there, is this vacuum system seperate. Thanks again.

xdescrubx

Just a little update. My AC now works fine after fixing the leaking vacuum hose attached to vacuum canister located behind the front bumper. I also noticed the vacuum hose that is connnected the heater valve was loose, which led me to find that the valve was sticking. So I replaced that, no more ac problems now. Hope this helps someone else.