1988 Cherokee AIR SYSTEM PROBLEMS

My air controls do not switch at all from defrost. The heat to air slider works just fine, and I'm sure the AC is out of freon so I don't expect cold air. I haven't worked with this system before. Please help. Thanks.

The airflow controls are actuated by vacuum. If you get air out the defrost vents only at all settings then you have a lack of vacuum to the controls. Major suspects are a cracked vacuum canister (inside the front bumper, passenger side) or the lines running from it located beneath the battery tray. Does your 4 wheel drive engage? It is also vacuum acuated by the control on the front diff beneath the oil filter. If it doesn't, that would confirm a vacuum problem.

Was doing some bumper work and noticed that the vacume line for the HVAC controls (small) was pinched and cut, near the vacume resivoir. On another occasion the big vacume line was, cracked and rotted under the battery tray. On another XJ, the vacume line plug, had come loose at the control unit (after a radio install).
Had some other vacume issues (serious vacume leaks), at the motor, that also seemed to influance HVAC operation.

Thank you so much guys I'll get out there tomorrow and check things out. Actually it's possible that the 4WD isn't working. I just picked up the XJ and it's been badly abused. The 4WD light doesn't come on at all either. This might explain that.

OK i found a vacuum hose (red one in engine bay) unattached and so i reattached it. Now the 4WD light is on constantly. I looked for pinched hoses etc in the engine bay and under the vehicle, I'm left with behind the dash now.

check the vacuum lines under the battery. they usually break from the battery acid. if the 4wd light stays on the 4wd switch in the transfercase sticks. it needs to be replaced.

OK here's the problem, there is no vacuum ball anywhere near the bumper. Nor are there any vacuum lines going underneath the battery tray. The only vacuum lines I have are the five colored hoses (red/green/blue/yellow/white) that are under the coolant res. On an 88 is there supposed to be a vacuum ball? I know this vehicle had a front end collission before I owned it. Possibly the previous owner just removed it altogether. I'm afraid this might be why I have no A/C and the vents don't switch from defrost! Also, the red vacuum line is connecting to a Y connector (with the inputs being the red hose, and a hose attached to the top of the engine on top of fuel injector plate) with the output attached to a long hose going nowhere. Is this correct?!

Dan answered his own question about the vacuum line colors at http://www.naxja.org/forum/showthread.php?t=29184

JKooshTJ said:

On an 88 is there supposed to be a vacuum ball?

Click to expand...

Yes, there should be one. Stock location is right side, inside bumper.