I have an issue that been bothering me lately since I got this XJ about a month ago. My a/c acting weird sometimes. When I use the a/c in rain or hot evening, it makes a spot in the middle of my front window have a cold fog spot. It seem like it leaking cold ac from the def vents. What could cause this?

Another a/c issue. Sometimes the climate control switch, the one in the middle where you can turn on and have diff selections. Sometimes I feel like it blocks cold air and slow down my fan speed than it really is. It on and off, sometimes it works fine and blowing very cold and sometimes it just slow down and blows very slowly. Is this vaccum issue?

 

My only two cents is that I know stuff (im pretty sure water) can condense in the lines and come out..Idk if that explains anything..I personally was a little confused on your question..its probably just cause im tired. haha

 

Oddes there there is a "hot spot" being created by either engine or something or a an air leak allowing the humidity to accumulate in a spot. Ac is just a dehumidifier, nothing else so it will do it's job and pull humidity out of the air

 

So, cold inside and hot spot from the outside is causing this spot?

 

I suppose there is a chance it's actually coming out of the vents, u can lay a towel over them to prove that theory

 

I'll bet the foggy spot is on the outside of the glass.....and yes, it's from a leaky defrost vent. Could be a vacuum leak and/or bad selector switch.

 

The spot wipes off from inside I bet, the "leak" would be hot, humid air leaking in to the cab and hitting the cold glass: either a dash leak or a windshield gasket leak or even a substantial leak any where but if that were the case you would probably see water somewhere.

It also could be just be that damn hot & humid and the defrost vents not closing correctly, cold air on hot glass. Think about a beer can...... Crap that reminds me, I need a beer!!

 

The spot wipes off from inside I bet, the "leak" would be hot, humid air leaking in to the cab and hitting the cold glass: either a dash leak or a windshield gasket leak or even a substantial leak any where but if that were the case you would probably see water somewhere.

It also could be just that damn hot & humid air and the defrost vents not closing correctly, cold air on hot glass. Think about a beer can...... Crap that reminds me, I need a beer!!

 

2 beers? LOL

 

Is the heater core leaking coolant?

 

No leaking heater core but I just lifted up my passenger side floor mat and it little wet. I guess it leaking a/c water onto my passenger floor board..

 

Is the fog on the inside or outside?

 

Have you tried cleaning out the evap drain? Drain may be clogged up. I just cleaned mine this weekend, I had water leaking into the passenger carpet and the air was funky. Here is what I did https://www.cherokeeforum.com/f2/diy...1/#post1058245

Also sounds like you have a vacuum leak as well.

 

None of the pictures work tho.. :/

 

This may be a little late but here goes anyway in case you never got this figured out.

There's good news and bad news. These are the most likely causes.
The good news: The fog is caused by a leaky defrost vent which is because of a vacuum leak in the defrost/cabin actuator. This line runs next to or under the battery and around the battery is usually where the hole or crack will be. You should be able to run your fingers under the battery, feel the vacuum line there (its the only one that runs under the battery) and feel the hole in it. Replace the whole thing with some windshield washer hose in the same diameter and problem solved or you can just cover it with some electrical tape and be done with it. its not perfect but it does get the job done. the actuator itself may be bad. im not sure if a change in vacuum pressure for a prolonged amount of time can damage it but it can still work "funny" even after you fix it. throw the least amount of money at it first.

the bad news: the leak in your passenger side floor is a whole different animal that can remotely be related but it is more rare. that leak is more likely the cause of issues with the heater core. either the box itself is cracked or the evaporator drain is clogged and water is accumulating in the system and eventually leaking out from the point of least resistance.

bad news because if your box is cracked well...you will want to sell/wish you never bought your xj several times. you'll say it anyway.
you have to remove almost the entire dash to get that box out. again, start with the cheapest and easiest solutions first. compressed air in the evaporator line, jb weld on any obvious cracks on the box etc

the vacuum line/actuator causing the leaky vent which in turn causes the foggy windshield (because cold air constantly hits the window at the same time as going into the cabin) is a pretty safe bet as to the culprit

i am very confident that these are your issues

hopefully the leak in the passenger floor is NOT in fact the heater core and just the evap line or a leak from the door or windshield gasket...this is very common as well. im having these issues now and plan on resealing the windshield because thats where my leaks are coming from. just after redoing the headliner too.

good luck