Heat/AC Diagram needed

[89 MJ]

Only the defrost works in my MJ. 89 4.0. Does anyone have a diagram/schematics for the heat/AC system?

Thanks

[eaglescout526]

I had defrost for a long while until I discovered a broken vac line going to the reservoir in the bumper. Have you checked that line? Usually that is a culprit to having defrost only. 

[89 MJ]

9 minutes ago, eaglescout526 said:

I had defrost for a long while until I discovered a broken vac line going to the reservoir in the bumper. Have you checked that line? Usually that is a culprit to having defrost only. 

I will look into that! Thank you!

[thecodemonk]

This is most likely, as eagle said, a leaking vacuum line (on my XJ, it was a line along the passenger side that broke).  The HVAC blender is mostly vacuum operated and will default to defrost when there's a vacuum leak.

[89 MJ]

OK! Thanks!

Just now, thecodemonk said:

This is most likely, as eagle said, a leaking vacuum line (on my XJ, it was a line along the passenger side that broke).  The HVAC blender is mostly vacuum operated and will default to defrost when there's a vacuum leak.

 

[cruiser54]

[89 MJ]

27 minutes ago, cruiser54 said:

Thank you!

[Eagle]

Also check that vacuum reservoir behind the bumper for cracks.

[89 MJ]

Will do!

[buxmj]

This is something I need to look at, thanks for the diagram!  

 

Buck

[1989commanche]

Mine had rubbed through the bottom of the hard vacuum line near the firewall. Was hard to find. But A few inches of new line now the a/c works correctly and the air blows out where it is supposed to. 

[89 MJ]

7 hours ago, 1989commanche said:

Mine had rubbed through the bottom of the hard vacuum line near the firewall. Was hard to find. But A few inches of new line now the a/c works correctly and the air blows out where it is supposed to. 

I had a similar issue.