Very low air flow from vents - JeepForum.com
 
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post #1 of 12 Old 01-17-2020, 10:56 AM Thread Starter
JWELK
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Very low air flow from vents

Typically I use the A/C on recirculate. While driving the air decreases in volume and the fan noise increases. I hear actuators working when I move the control from defrost, floor etc, but very little air flow from any of them. Where should I start?
Thanks
Jim W

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post #2 of 12 Old 01-17-2020, 06:51 PM
TheBoogieman
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Vacuum line is most likely cracked or loose. I've had to fix that on several of my Jeeps. Typically the air will blow out of the defrost and not the vents, while driving. Check the rubber elbow connecters at the intake manifold and vacuum reservoir too.
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Originally Posted by jeepinmichguy_ View Post
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post #3 of 12 Old 01-18-2020, 06:09 AM Thread Starter
JWELK
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Thanks
Yes, that is correct. In fact, mine broke where it goes through the firewall. However this is not the case, there is no air flow or very restricted air flow from any of the vents. I can hear one of the pistons moving when I change from the various modes, but still no air.
One other thing, the fan occasionally fails to come on. I have replaced the relay, maybe a little improvement. Cleaned the ballast resistor, it was quite dirty. Not so bad considering 20 yrs of dust. If I hit the bottom of the heater box, the fan starts. But that does not change the air flow situation.
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post #4 of 12 Old 01-18-2020, 07:57 AM
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I'd be looking at the wiring for melting and make sure the actuator is working properly. A good time to clean the dirt out too.

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Originally Posted by jeepinmichguy_ View Post
TheBoogieman is a jerk.
03' Rubicon/Zone 4" coils with 1" spacers up front/Rancho shocks/5.13 gears-35" MTZs/BM brakes
99' XJ / 5.5" lift / Rancho shocks/33" DC Extreme country MTs. Jeep #18
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post #5 of 12 Old 01-18-2020, 08:31 AM
CJ7-Tim
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Logically, one would visually inspect and test the entire apparatus. Check/test for vacuum leaks causing partial operation or partial failure of the blend or mode doors, check/test for wiring issues causing low operating voltage, check/test the blower fan for wear/damage causing excessive drag or voltage draw. No one can say measure 6.3 inches down the blue wire and there is the problem, you have to diagnose the root cause.

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post #6 of 12 Old 01-19-2020, 07:46 AM Thread Starter
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Thanks @Cj7
"partial operation or partial failure of the blend or mode doors". Thats what I was looking for. Blower/Ballast resistor/voltage are fine. Blend door stepper motor may be an issue. My understanding it is electrical, not vacuum controlled. I can hear the mode doors moving when changing modes. But they do not redirect the air flow when it has failed.
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post #7 of 12 Old 01-22-2020, 12:09 PM Thread Starter
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Update. I have removed the lower plate under the steering wheel to access C201. Specifically the Pwr wire to the blend door motor. As the unit is working I have 12 volts. I'll leave the meter on and detemine if that is the failure or something else. The blend door is not vacuum operated, it is a stepper motor. The PCM counts the pulses from the motor and determines how far it should open. And yes, it is a "Hall Effect Diode" just like the CPS and CKS. The pulse is there, and I doubt it disappears, as it never gets that warm.
Another site states the problem could be that the blend door gets weak with age. And the fan bends it back and forth. They offer a metal door, and describe cutting out the bottom of the heater box and inserting their device. Which they claim is easier than taking apart the heater box. https://heatertreater.net/jeep-cherokee. Anyone hear of them? Tried their product(s)
I'll let you know the results of the blend door motor.
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post #8 of 12 Old 01-26-2020, 05:52 AM Thread Starter
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Update. The blower failure seems to be bad brushes, does anyone have a part number? Any recommendations on a replacement fan, or which one not to buy.
The damper behind the radio operates correctly. So its either the blend door or the activating rod from the stepper motor.
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post #9 of 12 Old 02-08-2020, 11:55 AM Thread Starter
JWELK
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Replaced the blower motor today. Ebay part number 4886150AA. Has more air flow than the one that was in there. Was able to remove it without disconnecting the A/C. Bit tough coming out, about 20 minutes. The new one slipped right in.
Tools needed
10 MM deep socket
11MM deep socket.
Took the A/C dryer off the bracket, as well as the PDC. Removed the overflow reservoir. And cut several cable ties.
I don't know if this will solve the air flow issue, but I should no longer have to kick the heater box to get the fan to run.
"BleepinJeep has a Youtube video
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post #10 of 12 Old 02-08-2020, 01:06 PM
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Quote:
Originally Posted by JWELK View Post
Another site states the problem could be that the blend door gets weak with age. And the fan bends it back and forth. They offer a metal door, and describe cutting out the bottom of the heater box and inserting their device. Which they claim is easier than taking apart the heater box. https://heatertreater.net/jeep-cherokee. Anyone hear of them? Tried their product(s)
I did that on my 2000' WJ that had an issue with the dual climate control. I used one of those electric hot knife craft tools and it cut through the box like melted butter. It smoked like HELL doing it though. I was born with zero sense of smell (Congenital anosmia), so I don't know if it stunk or not. Problem was solved and it took about 45 minutes. Much better than removing half of the interior like a heater core replacement.

Quote:
Originally Posted by jeepinmichguy_ View Post
TheBoogieman is a jerk.
03' Rubicon/Zone 4" coils with 1" spacers up front/Rancho shocks/5.13 gears-35" MTZs/BM brakes
99' XJ / 5.5" lift / Rancho shocks/33" DC Extreme country MTs. Jeep #18
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post #11 of 12 Old 02-08-2020, 05:17 PM Thread Starter
JWELK
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@TheBoogieman If it comes to that, I will use the hot knife as opposed to the Dremel. The smoke is temporary, the Dremel debris will last forever
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post #12 of 12 Old 02-11-2020, 05:57 AM Thread Starter
JWELK
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The air stopped flowing yesterday. Sooo it looks as if I'll be doing the heatertreater treatment.
I'll let you know. Probably order the stuff early March. @TheBoogieman , which hot knife did you use.
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