Jeep XJ AC Vacuum Issue Diagnosis and Repair

I outline how to diagnose an AC system vacuum issue and what parts to use for your Jeep Cherokee XJ. This particular model is a 1995 4.0L. These tips would work for any system that relies on vacuum actuators for the AC vents.

[@pedroortizsalcido]

Hole crap this is exactly what’s wrong with mine. The losing ac while accelerating is a dead giveaway. Thanks for the explanation!

[@PhysifistEngineering]

Awesome. Hope this helped you out.

[@randydavis8020]

Thanks for showing this. I found the line under my battery tray, going to the vac canister in the bumper broken in half. I spliced it back in and my 95 2 door Sport has blowing AC now! YAY!

[@PhysifistEngineering]

Dude that's awesome! That's like the same feeling I had.

[@rudyduarte1809]

I never new about the canister under the bumper,I’m going to check it out,thanks for the help.

[@pauldolan1493]

I’ve never had a vehicle that utilizes vacuum for HVAC and did both heater core and evaporator yesterday. Yikes. Feel like I got in deep. Mines a 96 and while there was a learning curve, it wasn’t as bad as others I’ve had to pull dashes on. Thanks so much for you video

[@justinesimon7955]

oh and Thats the reason why my jeep was hard to start! a machanic wanted to charge me $100's and he said the starting issue had nothing to do with this. so you just saved me a ton of money!! your awesome! cheers!

[@swidahooverlanding2867]

I lost good A/C last summer in my 91. Still cooled but not as good as it was. I did notice that driving down the freeway if I started to pull a incline the vent would switch to the defrost. I did a test on the vacuum line, but I still felt it was in the vacuum system since the freon level was good. Going to replace valves and check the lines closer now. Thanks for the video! George.

[@lobomexicanocamping4241]

I just saved a lot of money watching your video, thanks a lot

[@markdicicco6409]

Ill be looking into mine this weekend. Checked behind the dash already. Now because of your video i dont have to trace down which vacuum lines are associated witht he ac. Thanks again!

[@gorillaswithbeards7411]

OUTSTANDING!!! GREAT VIDEO PERFECTLY EXPLAINED! THANKS FOR THE INFORMATION.

[@justinesimon7955]

Omg! thanks you SOOO much for this video. I have EXACTLY the same 3 issues you have atm with my 96.. gonna try today fix myself. i also just thought it didnt come with cruise control. 😕

[@paulkaufman4901]

Outstanding Video! You did a wonderful job of explaining what was happening and why. It was a great tutorial on vacuum systems. I sure hope my problem is that check valve on the intake because of accessibility 🙂

[@julianmartinez2885]

This video is very informative thank you

[@larrywarren1049]

Dude youre awesome I was ready to yank it out

[@IvanIvoMartinetti]

Cool, thank you for much needed info

[@harrykrix1106]

Thanks! great tutorial

[@erichunley595]

Great video, thanks for the help. My AC shuts down when accelerating or driving up hills on the highway, just bought the check valves, fingers crossed. Was having difficulty finding the right part numbers, thanks again. Kudos man!!

[@PhysifistEngineering]

No problem, be sure to check for any cracks or leaks in the engine bay. If that looks good and your valves are right, it may be a leak under the dash which is not fun.

[@JesusGarcia-lr2iu]

Great video 👍👍

[@kimlamminh]

Great video, thanks

[@Soothsayer-rs5nb]

Nice video

[@likewow3711]

thank you very much 😊

[@michellehammock3023]

That's a sweet Jeep

[@PhysifistEngineering]

You should see it now that I put some sweet bumpers on it.

[@ej9147]

for cracked hard vacuum lines, heat shrink tubing should work really well.....

[@PhysifistEngineering]

Yes, that would work great too.

[@mikealmiracle4834]

Dude…thank you

[@codynation1206]

Ok at 3:33 he's pointing at a hard line, I need to replace that entire line, how do I do that

[@take_a_tacoyt6502]

Those lil funny side comments 😂👌🏼

[@jilljackson939]

Nice jeep

[@PhysifistEngineering]

When did you get so political?

[@dangerclosegamingbf2366]

Nice video. did it have anything to do with being able to control the 'mode' settings like from floor to defrost to vent with regular heat? I am unable to redirect my heat from floor to anywhere else atm. I am fixing my 95 grand cherokee laredo with manual heater controls.

[@chriswalters6792]

blend door actuator most likely

[@dangerclosegamingbf2366]

@@chriswalters6792 LOL yes it was. The linkage had slipped off and needed to be reattached. Routing a CB antennae cable through there must've caused that.

[@DigitalDecayz]

I've got a 99 and I can't seem the find the 2nd vacuum check valve on the passenger side. My AC started coming through the defrost under load after i replaced the elbows (it was working before this, should've just left the disintegrating elbows alone I guess lol) and check valve on the intake manifold. All the lines check out and the check valve is facing the correct direction so I think the long elbows are just collapsing under the vacuum at load. I'm going to try and rev it in park to see if they collapse and if that's inconclusive maybe I'll cut the elbows a lot shorter to try and give them more structural integrity.

[@PhysifistEngineering]

Have you looked for a vacuum diagram for your year? It might be different. Also, have you verified that the check valve is good? And do you have a vacuum canister? Also verify that you don't have a vacuum leak on something else. Have you verified if you have any leaks under the dash like the lines going to the valves that control the ducting? Just trying to throw some ideas out there.

[@joannasbeautyx3]

For some reason mine isn’t coming out on high speed like it used to , it gets cold and comes out but the pressure doesn’t change from hi to lo

[@ky0611]

What should I do if I don't have a cruise control? I know a line runs into there

[@eusebiorodriguez4492]

I have a 1993 XJ, do you think those check valve part numbers will work on my year? Thank you

[@ralphnabozny8494]

my 92 cherokee had the cracks on that weeny hose .I found fish aquarium hose to couple it together. ac conditioning still not working. I drove for 7 years with out air conditioning. I had a guy put freon in and it lasted 2 weeks. May be another vac tube. every thing takes me 5 trys. :)

[@PhysifistEngineering]

Define not working.

[@patjones3520]

Did you take the little holder of the shifter or did it come like that mine is such as pain in the ass always moving around when I shift

[@PhysifistEngineering]

I removed the center console and I'm just running a boot over the shifter. The plastic was all cracked and this just looks cleaner.

[@daveg4963]

How was your idle before and after? Also, did you find a leak on the AC system?

[@PhysifistEngineering]

It's smoother, the engine starts quicker and the off idle response is more positive. I'd like to think efficiency would go up but I didn't test mpg before and after.

[@randomcitizen2384]

My small line going into the firewall for the AC system became disconnected and was hanging into the engine bay. How do you reconnect it?

[@PhysifistEngineering]

Check this post. Scroll down a little and it has 2 diagrams that show where the line attaches to the back of the under dash AC unit. May have to pull that assembly. Or make a hard line with a rubber end and maybe you can feed it through the hole and get it to slide onto that nipple. www.cherokeetalk.com/threads/vacuum-lines.26450/

[@wyattandwill12]

Well um I think I found my HVAC control issue 👍🏻 That T where it goes to the firewall with the check valve inline, my line is missing from where it gets thinner after the T down to about 2-3 inches from the firewall. No check valve left unfortunately

[@earlgeorge7573]

what year is this XJ that you are working on?

[@BradMillsOK]

So at the check valve at the manifold, air should be allowed to flow into the manifold and not backwards?

[@PhysifistEngineering]

Yes, the engine is creating the vacuum that is needed to run vacuum accessories. Without the check valve, all the vacuum you built up would go right back into the engine and you'd lose accessory function.

[@BradMillsOK]

@@PhysifistEngineering thank you! Replaced it about 30 minutes ago and now don’t lose vents under load. Yea!!!

[@powdere4donuts]

Hello, what if my ac blows, however when i switch it to heat, nothing happens and it stays cold. Pretty sure my defroster doesn't work either.

[@PhysifistEngineering]

Sounds like it could be the control panel, or the connections behind it. I'm sure someone has a video about it on here. I haven't run into that issue.

[@powdere4donuts]

@@PhysifistEngineering could be. Sometimes the ac stops working when i go over a bump

[@rennoc5547]

Would this also fix a heat issue?

[@PhysifistEngineering]

This would be for diagnosing the vent system so whether it's heat or ac wouldn't matter. If your blower function works but it's not hot it could be a clogged heater core or bad control valve.

[@baldomerogarza1458]

Man I wish I knew where that line went behind the firewall to replace. I’m sure I have more leaks on the vacuum line but can’t find anymore cracks

[@billleitz9150]

It went the same place mine did in side the firewall . i just pull the hole dash out to get to it and found the new lines at oriel's auto . Its going to take me about a day to do the work . good luck with yours .

[@PhysifistEngineering]

Scroll down a little and it has two diagrams that show where the line goes into the dash. www.cherokeetalk.com/threads/vacuum-lines.26450/

[@PhysifistEngineering]

You might be able to run a hard line through the firewall with a rubber fitting at the end and maybe get it to slide onto the nipple.

[@billleitz9150]

@@PhysifistEngineering i tried that and it only cracked again . But Thanks .

[@PhysifistEngineering]

@@billleitz9150 you'd have to remove everything attached to the nipple and run fresh hardline. Might find it at the parts store.

[@ColeBabyZimmer]

What do the check valves do?

[@PhysifistEngineering]

They allow the system to hold a vacuum by only allowing the air to flow one way.