99 Cherokee HVAC Problem
 

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 ±
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

Re: 99 Cherokee HVAC Problem
 

Hi Janie,
All manufactures design their computers to shut the air conditioner
off if the engine is in danger of over heating. Maybe, add an auxiliary
transmission cooler if you're going to haul a trailer again.
God Bless America, Bill O|||||||O
mailto:-------------------- http://www.----------.com/

JB wrote:
>
> 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 ±
> 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

Re: 99 Cherokee HVAC Problem
 

Hi Janie,
All manufactures design their computers to shut the air conditioner
off if the engine is in danger of over heating. Maybe, add an auxiliary
transmission cooler if you're going to haul a trailer again.
God Bless America, Bill O|||||||O
mailto:-------------------- http://www.----------.com/

JB wrote:
>
> 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 ±
> 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

Re: 99 Cherokee HVAC Problem
 

Hi Janie,
All manufactures design their computers to shut the air conditioner
off if the engine is in danger of over heating. Maybe, add an auxiliary
transmission cooler if you're going to haul a trailer again.
God Bless America, Bill O|||||||O
mailto:-------------------- http://www.----------.com/

JB wrote:
>
> 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 ±
> 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

Re: 99 Cherokee HVAC Problem
 

Hi Janie,
All manufactures design their computers to shut the air conditioner
off if the engine is in danger of over heating. Maybe, add an auxiliary
transmission cooler if you're going to haul a trailer again.
God Bless America, Bill O|||||||O
mailto:-------------------- http://www.----------.com/

JB wrote:
>
> 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 ±
> 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

Re: 99 Cherokee HVAC Problem
 

"JB" <janie557@hotmail.com> wrote in message
news:1153720065.401864.220210@i3g2000cwc.googlegro ups.com...
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 ±
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

My wife and I have twin 1999 Jeep Grand Cherokees. Mine has no problems, as
you describe, but her Jeep has the same problem. Since they are both over
our 60,000 mile warranty, I found a cheap (meaning no money) fix. I put her
control (on the right hand side) to the upper vents, for air conditioning
(in the summer) and leave it there, never turning it to the off position.
It takes maybe 10-20 minutes for the baffles to "set" but once they do,
there they are. When heating season comes, change to the down (or up and
down) position and it will take another 10-20 minutes to "set' but there you
are. Never put it in the "off" position.

I don't know if the Grand Cherokee system is the same as the Cherokee, and I
don't know much, but that's what know, and hope it can help.

Re: 99 Cherokee HVAC Problem
 

"JB" <janie557@hotmail.com> wrote in message
news:1153720065.401864.220210@i3g2000cwc.googlegro ups.com...
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 ±
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

My wife and I have twin 1999 Jeep Grand Cherokees. Mine has no problems, as
you describe, but her Jeep has the same problem. Since they are both over
our 60,000 mile warranty, I found a cheap (meaning no money) fix. I put her
control (on the right hand side) to the upper vents, for air conditioning
(in the summer) and leave it there, never turning it to the off position.
It takes maybe 10-20 minutes for the baffles to "set" but once they do,
there they are. When heating season comes, change to the down (or up and
down) position and it will take another 10-20 minutes to "set' but there you
are. Never put it in the "off" position.

I don't know if the Grand Cherokee system is the same as the Cherokee, and I
don't know much, but that's what know, and hope it can help.

Re: 99 Cherokee HVAC Problem
 

"JB" <janie557@hotmail.com> wrote in message
news:1153720065.401864.220210@i3g2000cwc.googlegro ups.com...
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 ±
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

My wife and I have twin 1999 Jeep Grand Cherokees. Mine has no problems, as
you describe, but her Jeep has the same problem. Since they are both over
our 60,000 mile warranty, I found a cheap (meaning no money) fix. I put her
control (on the right hand side) to the upper vents, for air conditioning
(in the summer) and leave it there, never turning it to the off position.
It takes maybe 10-20 minutes for the baffles to "set" but once they do,
there they are. When heating season comes, change to the down (or up and
down) position and it will take another 10-20 minutes to "set' but there you
are. Never put it in the "off" position.

I don't know if the Grand Cherokee system is the same as the Cherokee, and I
don't know much, but that's what know, and hope it can help.

Re: 99 Cherokee HVAC Problem
 

"JB" <janie557@hotmail.com> wrote in message
news:1153720065.401864.220210@i3g2000cwc.googlegro ups.com...
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 ±
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

My wife and I have twin 1999 Jeep Grand Cherokees. Mine has no problems, as
you describe, but her Jeep has the same problem. Since they are both over
our 60,000 mile warranty, I found a cheap (meaning no money) fix. I put her
control (on the right hand side) to the upper vents, for air conditioning
(in the summer) and leave it there, never turning it to the off position.
It takes maybe 10-20 minutes for the baffles to "set" but once they do,
there they are. When heating season comes, change to the down (or up and
down) position and it will take another 10-20 minutes to "set' but there you
are. Never put it in the "off" position.

I don't know if the Grand Cherokee system is the same as the Cherokee, and I
don't know much, but that's what know, and hope it can help.

Re: 99 Cherokee HVAC Problem
 

Your vacuum reservoir is collapsed, or there is a vacuum leak.

Earle

"JB" <janie557@hotmail.com> wrote in message
news:1153720065.401864.220210@i3g2000cwc.googlegro ups.com...
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 ±
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