'97 XJ Vent problem

My boss at work has a ,97 xj. Last spring I helped him out fixing a vacuum leak. He had spilled some kind of cleaner on the vacuum line behind the battery and it ate a hole right through it. At the time, he noticed that his vents had stopped working. He cut out and fixed the bad vacuum lines, but he is still having prblems with the vents intermitantly. Now the vents will stop working whenever he is pulling a grade. He also noticed that the vents will occasionally switch to defrost. I'm guessing that it is still a vacuum problem. Is there anything particular I should check? Anything else this could be? Thanks for any help.

Check this thread, seem to remember it was discussing that issue..

Vacuum Thingy

There is a small vacuum line that penetrates the firewall near the A/C lines on the passengers side which supplies vacuum to the climate control dampers.... The line should have a check valve in line so that when you climb a grade on the highway your dampers will continue to have vacuum by shutting off the vacuum on the upstream side of the system to maintain a vacuum on the dampers. This is assuming you dont change positions yourself which will deplete the trapped vacuum in the lines on the downstream side of the check valve. If you dont have a check valve.... you should....
Couldn't hurt to look for more vacuum leaks.....
Mighty vac vacuum pump works great for troubleshooting vacuum leaks in lines....

Charles

the 97's had a problem with the doors insidt the heater case. the proper fix is to replace the upper half of the heater case. jeep issued a tsb for this.