A recent 300 mile camping trip pulling a small tent trailer afforded an opportunity to better characterize the problems with the HVAC of our
1999 Jeep Cherokee. We'd taken it in the week before our trip with a complaint that the ventilation would randomly shut off the vents although the fan continued to run. Our repair shop found a technical service bulletin that was relevant, diagnosed a failing panel vacuum actuator, and replaced the unit.However, on our trip we had the same problem but now were able to observe that the ventilation shuts down under conditions of high manifold pressure (e.g., going up hill) but the ventilation was restored on level or downhill grades. Rapid acceleration on level ground also caused the ventilation to shutdown.
This behavior was consistent regardless of whether the air conditioner was selected or just simple fresh air ventilation. We did not check whether it occurred when the selector was positioned for defrost.
A possibly related problem is occurring with the "factory installed" cruise control. It used to be quite solid, keeping the speed within =B1 one mph--now it has a good five to ten mph slop and can take tens of seconds to resume the set speed.
Fuel consumption has remained constant, we continue to get 20 mpg, in-town and on the highway with or without the trailer. I have noticed that the engine seems to have some hesitation and not quite the same acceleration lately but it is approaching 90,000 and is time for service.
Any help would be appreciated.
Janie