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AC blows less air when cruise is on

FlexdXJ

FlexdXJ

NAXJA Forum User
NAXJA Memorial Lifetime Member
Location
Columbus, In
Like i said I noticed today that when my cruise is on at 70 mph on the interstate the AC seems to blow less air. I am assuming the cruise is drawing vacuum causing the blend doors to close. How can I solve this issue? I searched and couldn't find what i was looking for.
 
I would love to know about this too. I've made sure the hose line is connected to the ball under the bumper and I've traced the line through the engine bay and didn't notice any holes.
 
kdailey4315 said:
I would love to know about this too. I've made sure the hose line is connected to the ball under the bumper and I've traced the line through the engine bay and didn't notice any holes.
Click to expand...

I relocated the vacuum bulb to under the hood when I put my JCR bumpers on. I will check the line for cracks but i'm not sure thats the problem. I am wondering if one of the bigger vacuum bulbs would help me. Mine had the small one on it when I bought it though.
 
The blend door is not vacuum actuated. However, when it does it again, see if you feel anything out the defrost vents.
 
Saudade said:
The blend door is not vacuum actuated. However, when it does it again, see if you feel anything out the defrost vents.
Click to expand...

I didn't know that! I will check the defrost vents next time. It has to be vacuum related because it only happens when the cruise is on. Works fine the rest of the time.
 
The "mode" doors are vacuum operated (floor, dash, defrost). So possibly some of the air is diverting to the defrost under low vacuum so it feels like less air blowing out the dash vents.
 
Saudade said:
The "mode" doors are vacuum operated (floor, dash, defrost). So possibly some of the air is diverting to the defrost under low vacuum so it feels like less air blowing out the dash vents.
Click to expand...


You could be on to something. I didn't even think of checking the defrost vents yesterday as i was driving. What could fix this issue easily? I am driving 5 hours to the Cherokee Crawl In a couple weeks so i'd like to fix it by then.
 
I'd look into using two separate vacuum canisters-- one to operate the cruise and a second one for the HVAC.

hang 'em off the rear bumper and you'll have trucknutz:rof:
 
If this is the case, then you may likely have a vacuum leak. This could show up more when climbing up hills on cruise control because the engine is not developing a lot of vacuum and the CC actuator is vac operated.

Double check all the lines. Pay particular attention around the battery box if there are still lines around it (I see you relocated the ball).

What RPMs are you running @70?
 
Shorty said:
I'd look into using two separate vacuum canisters-- one to operate the cruise and a second one for the HVAC.

hang 'em off the rear bumper and you'll have trucknutz:rof:
Click to expand...

You are on to something! :D

Saudade said:
If this is the case, then you may likely have a vacuum leak. This could show up more when climbing up hills on cruise control because the engine is not developing a lot of vacuum and the CC actuator is vac operated.

Double check all the lines. Pay particular attention around the battery box if there are still lines around it (I see you relocated the ball).

What RPMs are you running @70?
Click to expand...

It seems like it still blows steadily I hadn't noticed too much difference between going uphill and going downhill( not exactly hilly between here and indy though). There is no longer a line running under the battery tray. It runs around 2200 rpm at 70mph.
 
FlexdXJ said:
You are on to something! :D

It seems like it still blows steadily I hadn't noticed too much difference between going uphill and going downhill( not exactly hilly between here and indy though). There is no longer a line running under the battery tray. It runs around 2200 rpm at 70mph.
Click to expand...

Even if you have a small leak in the vacuum system there should be a check valve in the line supplying the climate controls. The purpose of the check valve is ensure the climate controls stay in the last position they were placed in during low vacuum situations.
This was found to be a problem on the '97s and early '98s and was resolved by installing the check valve. I had to install a check valve shortly after purchasing my XJ in Oct '97.
The check valve should be installed in the vacuum line near the refrigerant accumulator/drier before it goes thru the firewall.

At 70 mph my engine RPM is 2850 with 4.56s, 32" MTRs and AX-15.
 
CharlesS said:
Even if you have a small leak in the vacuum system there should be a check valve in the line supplying the climate controls. The purpose of the check valve is ensure the climate controls stay in the last position they were placed in during low vacuum situations.
This was found to be a problem on the '97s and early '98s and was resolved by installing the check valve. I had to install a check valve shortly after purchasing my XJ in Oct '97.
The check valve should be installed in the vacuum line near the refrigerant accumulator/drier before it goes thru the firewall.

At 70 mph my engine RPM is 2850 with 4.56s, 32" MTRs and AX-15.
Click to expand...


I could be wrong but i am pretty sure there is a check valve there(that may have been my first XJ, i haven't paid that much attention). I'll check that out and if it doesn't i know there is one on the comanche i can rob.

Charles, i also have 32's but with stock gears and AW4. So it looks like i should be somewhere around 2500 at 70 with 4.10's.
 
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