ricksjeepster Posted March 18, 2012 Share Posted March 18, 2012 hello my mj has this "air" issue when I turn on the a/c it works fine but the air goes to the upper vents resulting in a very cool windshield. somebody have a picture or diagram of the vacuum lines that control the direction of air flow? Thanks :wrench: Link to comment Share on other sites More sharing options...
mvusse Posted March 18, 2012 Share Posted March 18, 2012 Without vacuum, it defaults to the defog vents. Your problem is a broken vacuum hose somewhere, Link to comment Share on other sites More sharing options...
HOrnbrod Posted March 18, 2012 Share Posted March 18, 2012 Follow the vacuum along the right side of the engine compartment forward where it goes through front bulkhead near the battery to the vacuum canister behind the bumper. They usually break in that area. Link to comment Share on other sites More sharing options...
ricksjeepster Posted March 18, 2012 Author Share Posted March 18, 2012 yeah already did check the vacuum canister lines they are fine what I'm looking for is a pic or diagram to find out what line is missing cause i have no line coming from the right side of the engine or air filter box... Link to comment Share on other sites More sharing options...
adam518 Posted March 18, 2012 Share Posted March 18, 2012 A bad check valve can cause the same issue under load/acceleration. Mine would blow fine normally but default to the defrost vent when accelerating or going up a hill. It turned out both the vacuum check valves were bad. Link to comment Share on other sites More sharing options...
carnuck Posted March 18, 2012 Share Posted March 18, 2012 Look above the gas pedal for a hose off. 8 XJs and 3 MJs so far with that issue. Link to comment Share on other sites More sharing options...
ParadiseMJ Posted March 18, 2012 Share Posted March 18, 2012 yeah already did check the vacuum canister lines they are fine what I'm looking for is a pic or diagram to find out what line is missing cause i have no line coming from the right side of the engine or air filter box... If you are looking for a vacuum SOURCE from the air filter...it's not there. The HVAC are on lines on the passenger side firewall coming out of a little rubber grommet...one pink or tan...one black. The tan or pink one should go to the heater control valve. The black line goes to the vac ball behind the front bumper. The vacuum SOURCE comes from the intake manifold across to the cruise servo (if equipped) and to the bigger line on the vac ball. It seems that the Source line goes in then out of the cruise servo and T's off to both sides of the vac ball. I have cruise so I have the football shaped one. My 88 has no cruise and just has the softball sized one The hose with the brass fitting on the manifold goes to the vacuum ball (I relocated it to the engine compartment) and provides the source vacuum. The heater control valve is supplied vacuum with the pink line. I have an HO valve and swapped to an open system. The heater control valve is gone now and the pink line is plugged with a cap. The small black line (next to the pink line) that comes out of the firewall goes to the ball. That line controls all your HVAC needs. Link to comment Share on other sites More sharing options...
jpdriver1 Posted March 18, 2012 Share Posted March 18, 2012 let me be the first to thank you for the pics -- my 89 has this same issue, plus the cruise is not working --- for now 8) Link to comment Share on other sites More sharing options...
ricksjeepster Posted March 20, 2012 Author Share Posted March 20, 2012 Paradisemj thanks for the [pics !!! great help my friend, everything is working porperly now... My MJ is ready now for this net summer in Baja... Problem was I wasnt getting any Vacuum from the manifold, since I did an entire swap from 4 cyl to 6 cyl and took off the entire wiring and harness I guess I forgot to connect that line into the manifold bottom line Thanks to everyone for your help and to paradisemj for the pictures!!! :cheers: Link to comment Share on other sites More sharing options...
ParadiseMJ Posted March 20, 2012 Share Posted March 20, 2012 Glad you got it going. Helping is what the forum is all about...oh, and screwing around. :cheers: Link to comment Share on other sites More sharing options...
relyt120 Posted March 20, 2012 Share Posted March 20, 2012 I had this same problem last week, reconnected the vacuum hose and everything was fine :thumbsup: Link to comment Share on other sites More sharing options...
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