Now For A Challenge!! Intermittent HVAC issue

[a.mohamed84]

Hi everyone, Im Adam and I have a INTERMITTENT problem with my fiancees 2001 SSEi. First off, I want to point out that this car has always gotten the best of care and it shows The car is nearly mint and is detailed by-weekly!! My fiancee and I hate it when something goes wrong with the "Bonnie"; it drives us nuts until its resolved and the latest issue has thrown me for a bit of a loop!

At times, little to NO air will come out of the vents and other times, everything is good. I played with recirculation and fresh-air controls, different modes and checked the cabin filter to no avail.

Is there a electronic vacuum control valve under the dash or in the engine-bay that could be periodically malfunctioning? I doubt there is a vacuum leak because of the intermittent nature of this problem. When the air is pushing out of the vent, it is only a matter of time before the pressure drops and soon air is barely felt. Sometimes the pressure is good for about 45 minutes before it starts to die down.

Winter will be here soon and I want to make sure the climate controls are good for defrost and heating during the cold months.

The blower fan works fine, and I can hear the actuators moving between all the mode selections which is great.
Can someone tell me what the issue is here? I'd prefer not to resort to disassembling the dash and chasing a whole bunch of dead ends.

Any help would be greatly appreciated. The car is a daily driver and cannot be subjected to long periods of downtime :S

Thanks in advance

Adam & Melanie

[Archon]

Is the air perhaps being directed somewhere else, like to the floor?

All actuators are electronic. None are controlled by vacuum. There is one for each side to control the temperature, one to direct where the air goes, and another to change between recirculating and outside air.

Perhaps there is a problem with the mode actuator.

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[a.mohamed84]

Thanks Archon for your reply and for the pic, it is very informative

So you're telling me that if the directional motorized actuator is malfunctioning and cuts out, it becomes disengaged, ceases to push air out the circular dash vents and air would be directed somewhere else like to the floor vents under the dash?

I didn't notice feeling air at my feet when this air problem arises, but its possibly an oversight on my part.

I will check it out and let you know what I find.

In the mean time, could you entertain the scenario that when the air stops pushing out the circular vents as desired, air isn't exiting out any other vents? I only ask because when the issue happens, I notice the blower fan becomes louder...howls more

Thanks again

[bobgto65]

Everything is controlled by the climate control unit and the instrument panel module. These are not a common parts to go bad. But this sounds complicated and you may have to nring the car to the dealer so they can scan the system and find out what is causing the problem. Also have you been changing the cabin air filter? If not, replace this and see what happens.

[a.mohamed84]

Hello again:

I talked with Melanie and she tells me that when the air cuts out, no air can be felt anywhere else. switching between modes such as defrost and floor doesn't change the dropped air pressure problem.

We brought the car to the GM dealer and the technician never mentioned being able to scan the cars system to pinpoint any problem areas; he just said he could pull out the cabin filter and inspect its cleanliness and that anything more would require disassembling the dash and will cost time and $$$

The cabin filter is changed regularly and is inspected by myself at every oil change, which occurs every 3 months

Perhaps the issue is with the climate control unit and or instrument panel module??? I hope not

[bobgto65]

I have the 2004 service manual and the HVAC is essentially the same. Under the section for "AC Delivery Improper" the first step is to use the scan tool to recalibrate all the actuator motors and look for DTC's in the IPM. Then you check blower motor speeds and check the ECC Mode switch to see if the air goes to the right places in all the modes. The scan tool checks the correct parameters for each mode. Then there are several circuit tests, Ignition 3, Low reference for mode actuator and 5V reference for mode actuator, checking for poor connections at the mode actuator, replacing the mode actuator, replacing the HVAC control module, and replace the IPM.

[redzmonte]

when the air stops blowing out the vents, do you still hear the blower motor running? if it dies out then your probably looking at a motor (gets hot and dies). If it blows but no air comes out then i would think the air blend door accuator might be failing. Just for grins, you might try swapping the relay for the air system, could be getting hot and failing as well (its free and easy, worth a shot)

Might want to start by removing the glove box and checking the air blend doors when it stops working..

S

[a.mohamed84]

Hey everyone, thanks for the Shop Manual walk-through (I will take this to the GM dealer and tell em to pull up their socks!)

Yes, the motor still works fine, so I will try the relay swap and open the glovebox n have a peek

Thanks again for all your help guys, I will let you all know what I have figured out

[Archon]

I can't think of any of the actuators that would totally stop the air flow. If it was one of the air mix actuators, it may affect the temperature you get, but the air would continue to flow. Same with the mode actuator. It may change where it goes, but that's about it. The last one changes whether you get outside air, or recirculates through the car but again shouldn't stop the air flow. The only thing that I can think of is that something has broken loose, or gotten sucked into the duct and somehow manages to block it intermittently.

[xdhd350]

I have this EXACT SAME problem with my 2001 SSEi. Unfortunately, I haven't found the cure for it either. It's just as the OP described, somewhere at a time and place of its own choosing, you'll notice no air coming out of the upper vents. The blower motor will make a somewhat louder growl during this time.

It's not the blower motor, because I had to change my original motor due to a different problem, and this issue continues with the new motor.

It won't do this all the time and I have cycled it between every mode and ran the temps full hot to full cold and it doesn't help. You hear the motor running, but no air comes from any place you put the mode selector to. Hard to diagnose when it's so intermittent.

Greg

[chevychev]

I'm with Archon on this one. If airflow output is dropping there has to be something blocking the airflow. You might be able to feel around going through the filter housing. I can't remember if you can actually see the blower motor through this access or not but if you can, and the car is doing it you can try removing the filter and watching what is happening with the blower that might explain the difference in sound. Obviously take the necessary safety precautions before reaching inside.

[xdhd350]

I'm with Archon on this one. If airflow output is dropping there has to be something blocking the airflow. You might be able to feel around going through the filter housing. I can't remember if you can actually see the blower motor through this access or not but if you can, and the car is doing it you can try removing the filter and watching what is happening with the blower that might explain the difference in sound. Obviously take the necessary safety precautions before reaching inside.

The problem is that it's intermittent. I've already replaced the blower motor that died after water got into it from a plugged drain tube under the car. Yes, when you remove the HEPA filter, you are staring down at the squirrel cage of the blower motor so you don't want to reach in with the blower running. My bet is that somehow, ALL the air doors are closing at the same time. It's weird. I would have suspected an ice ball in the evap core which would block air flow, but I've had the problem in the winter time as well.

The sound is hard to describe, but is likely due to a motor that has no place to discharge the air having higher air pressure on the rotor blades.

[mrwildroot]

Could the leads to the motor have been reversed when you replaced that blower motor assembly?
Reversing polarity on the motor could cause it to rotate in the opposite direction, sucking air out of the cabin instead of blowing air in. All dampers would be closed by air pressure.

Just a thought.

MW

[xdhd350]

Could the leads to the motor have been reversed when you replaced that blower motor assembly?
Reversing polarity on the motor could cause it to rotate in the opposite direction, sucking air out of the cabin instead of blowing air in. All dampers would be closed by air pressure.

Just a thought.

MW

Not possible to reverse leads as they are in a molded plug. Besides, this is an INTERMITTENT problem that comes and goes with no rhyme or reason just as the original poster stated. If it were even possible to reverse the motor leads, that would be a CONTINUOUS problem until the leads were reversed. 90 percent of the time, it works fine.

I only mentioned replacing the blower motor as proof that the problem is not the blower motor because the problem that I and the original poster reported has spanned 2 different motors in my car. I never considered it to be a blower motor problem anyway because you can hear the blower running even when no air is coming from vents.