1996 XJ Sport - The air distribution is stuck on defroster. Looking at the parts breakdown, I see the defroster, floor and dash panel vacuum motors, and I see the vacuum harness. Any experience with this problem? If there was a vacuum leak I think I'd have noticed a loss in engine performance and/or possibly have gotten some CEL code illuminate. Neither of those things occurred. I do not get the floor or the dash airflow, only the defroster. Is this a controller problem or am I looking at a vacuum loss that isn't significant enough to prompt a code or degradation of engine performance? If I deflect the visors downward the defroster cooling air can be effectively redirected towards the front occupants. Being 90-ridiculous degrees outside I'm waiting for the Fall (central Florida) to perform exploratory surgery on this problem. Thanks.

 

It's likely just a vacuum issue. If it isn't affecting the engine it isn't going to trigger a code. The codes exist to monitor emissions stuff - they could give 2 poops about whether your HVAC stuff is working or not.

Grab a vacuum pump from your local parts retailer and see if you can put vacuum on it where the line goes into the firewall on the passengers side of the engine compartment and operate the controls. (You may find it's even disconnected at that junction). It's possible there's something wrong with the control panel, but it's far more likely that it's vacuum related.

 

Thanks for that. Will do and report back what I find.

 

Starting at the vacuum source at the manifold, I found the vacuum hose just barely lodged into the rubber elbow sitting atop the plastic check valve. I seated it into the elbow and that restored normal vacuum pressure to the system. I have all the commanded positions of the controller again.