My ac, vent, heater, ect turns off when I get to about 45 miles an hour. Any idea's

 

drive under 45.

and give more details.

 

Does it do it every single time you hit 45? can you turn off the AC and then turn it back on at say 65? After you figure it out don't forget to post the solution. What year XJ?

 

The first place my mind goes when there is a problem with the heater/AC is straight to some kind of a vacuum leak. I know in my 2000 XJ when I gun it, it switches from the vents to defrost until I stop gunning it. I guess it does that because it loses enough vacuum that it goes to the default setting, which is defrost. So it could be that you have a small leak and when you go 45 mph you lose enough vacuum that it is switching to defrost. Next time it happens, put you hand by the windshield and feel for air coming out of the defroster. If that is the case, start looking for a leak. Its a long shot but that's all I can think of. Good luck.

 

That was my thought as well. I've seen other Chrysler AC systems do similar things because of vacuum leaks.

Are you saying it stops blowing out the vents, or that it just stops blowing cold? If it stops blowing out the vents, try feeling above the dash and see if it's coming out the defroster vents. If it is, look for vacuum leaks, starting at the vacuum canister in the front passenger bumper.

 

the vacuum pressure comes directly from manifold. the follow the lines to and from your "egg" (located inside the front passenger bumper.) and just unplug them, one by one, and blow. When you find one leaking, fix it or replace it. if it is your vacuum egg, replace it.

 

It's a 1990 xj. The air all together stops blowing out of the vents. I'll check all vacum lines and egg. does the the egg only have 2 vacum lines or 4? mine only has 2 but looks like there sould be 4.

 

There was a leak from the ac controls in the dash. I replaced the unit and it fixed the problem.