JPXJMOAB

Well my AC blows through the defrost while going up hills and under any sort of acceleration. I've replaced the vacuum line that goes to the canister and relocated it's.. Sprayed carb cleaner on the connections in the engine bay and can't find a leak. Any ideas where else to look?


Also, my AC blows colder at idle, but when driving down the road it doesn't seem to blow as cold, I just charged it a few weeks ago. Any suggestions?

DFlintstone

Kind of busy now. You are right on track. There IS c chack valve in thr cnister that makes the whole buisness work.

JPXJMOAB

So are you saying the vacuum canister itself could be bad?

CCKen

The check valve referred to may be at the tee where the vacuum tube for the HVAC control panel (not all XJ's have this check valve, or at the intake manifold. The one at the intake goes bad. You have to remove it and blow through it to see if it's stuck. It should be free flow one way and checked the other way.Mark which way the check valve is facing before removing it. See pics.


The '99 XJ does not have a check valve in the vacuum reservoir.


Tee at firewall:





Couple views of the check valve at the intake - hard to see in these pics but you'll know it when you look in this area.



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JPXJMOAB

I believe I only have the HVAC check ball. I'll give that a try when I get home in a few minutes!

JPXJMOAB

CCKEN, It did have a check valve near the intake manifold, it was flowing both ways, luckily I had an extra from my parts jeep so I'll report back on that tomorrow and see how it goes! Any suggestions on the AC being colder at idle?

travisrr

subscribed. I'm having the same issues

CCKen

Verify that the front of the condenser is not covered in mud, or other crap that would block airflow.


Recheck the refrigerant charge to see if it's still fully charged.


What setting do you have on your mode selector when this happens - MAX AC/Recirc or some other AC selection? When in MAX AC the recirculation door is open, bringing in air for the blower from the cabin, in any other C selection the Recirc door is closed and air is brought in from the outside. Try both ways to see if it makes a difference.


Your Blend-Air Door is electrically controlled by the temp selector on the HVAC climate control panel,


Here's a schematic that shows the functions (see pic). You can see if it is functioning by turning the key to RUN and looking up at the bottom of the Blend-Air Door Actuator, then moving the temp selector from full hot to full cold. The white intermediate drive shaft on the bottom of the actuator should move about 90 degrees each way.



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The intermediate drive shaft to the Blend-Air Door pivot shaft connection has been known to strip out, caused by a sticky door; where the motor is turning the intermediate drive shaft but the door is not moving.



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JPXJMOAB

I'll check fefrigerant levels today after work, as for what setting, I have it on recirculate..

JPXJMOAB

Just started driving to work & the AC is blowing out the defrost cents again, not under acceleration anynore, now it's just up and small/large hill. Sometimes it blows half defrost/half front vents.