2008 Yukon Denali AC issue: Is there a way to clean dust and debris of the evaporator? (AC acting screwy)

Gildan

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Is there any way to get at the evaporator on the AC system in a 2008 Yukon Denali to remove dust and debris without tearing the whole dash out of it?

Here's the issue. AC system was serviced, performed fine for several months. No leaks for coolant to get out, etc. Everything is fine. Compressor fined. System was cleaned and serviced top to bottom and no electrical/component/computer/etc., can be found.

AC is well sub par suddenly. If you turn up the fan to deliver cool air more than one or two notches the air temp goes from about 50-60 degrees F up to about 5 degrees below ambient outside air temps. Turn the fan down to the lowest setting and the air will get down to 40 degrees F. Turn it up any and the air out put goes up to 65-70 F. "Auto" feature is useless and simply does not cool at all.

Now here's the kicker: in order to get anything resembling feeble cool air you have to turn the fan down to nearly the lowest setting and thus disable the "auto" feature. Then you have to turn on the "Auxiliary" system for the rear passengers, and then, maybe, it might give you 60 to 65 degrees out of the vents.

The dealer claims that there is nothing wrong with the system and says I just have to live with the poor design and tough nuts there's nothing they can do. And they want a heap of money just to see if there is dust on the evaporator in the heater box area. It would be cheaper to just rip out the whole system, top to bottom and replace it all than just dust off the evaporator fins. And the dealer says that there is no guarantee that replacing the whole system will correct the problem and probably won't. Essentially they told me that the AC design for this year is just sub-par and there is no means to correct the issue. As a side note, the 2008 is the one year they do not have an air cabin filter in the system.

Now, the reason for me suspecting dust and debris in the fins of the evaporator is from a persistent issue with this vehicle (promise you all won't laugh at this one :p). I spend a lot of time in Northeast Arkansas where there is a lot of rice patties, which are flooded, which means that there are a lot of mosquitos. And I mean a lot of mosquitos. 100-200 mosquitos per cubic foot of air at night). So, I roll up the windows, turn on the AC on recirculate and when I do, mosquitos are expelled from the AC vents like a swarm of locusts to suck the occupants of the vehicle of blood like an infestation of vampires. I feel like I'm driving a vehicle designed by Alfred Hitchcock and having George Carlin riding shotgun at the same time.

I was thinking of dropping the kick guard, dropping the blowing motor and seeing if I could dust off the debris but I suspect the design engineers did something to preclude this remedy as per "Gray's Law'"*

*Gray's Law: "Incompetence carried to a sufficiently advance level is absolutely indistinguishable from deliberate malice."
 

swathdiver

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Is there any way to get at the evaporator on the AC system in a 2008 Yukon Denali to remove dust and debris without tearing the whole dash out of it?

Here's the issue. AC system was serviced, performed fine for several months. No leaks for coolant to get out, etc. Everything is fine. Compressor fined. System was cleaned and serviced top to bottom and no electrical/component/computer/etc., can be found.

AC is well sub par suddenly. If you turn up the fan to deliver cool air more than one or two notches the air temp goes from about 50-60 degrees F up to about 5 degrees below ambient outside air temps. Turn the fan down to the lowest setting and the air will get down to 40 degrees F. Turn it up any and the air out put goes up to 65-70 F. "Auto" feature is useless and simply does not cool at all.

Now here's the kicker: in order to get anything resembling feeble cool air you have to turn the fan down to nearly the lowest setting and thus disable the "auto" feature. Then you have to turn on the "Auxiliary" system for the rear passengers, and then, maybe, it might give you 60 to 65 degrees out of the vents.

The dealer claims that there is nothing wrong with the system and says I just have to live with the poor design and tough nuts there's nothing they can do. And they want a heap of money just to see if there is dust on the evaporator in the heater box area. It would be cheaper to just rip out the whole system, top to bottom and replace it all than just dust off the evaporator fins. And the dealer says that there is no guarantee that replacing the whole system will correct the problem and probably won't. Essentially they told me that the AC design for this year is just sub-par and there is no means to correct the issue. As a side note, the 2008 is the one year they do not have an air cabin filter in the system.

Now, the reason for me suspecting dust and debris in the fins of the evaporator is from a persistent issue with this vehicle (promise you all won't laugh at this one :p). I spend a lot of time in Northeast Arkansas where there is a lot of rice patties, which are flooded, which means that there are a lot of mosquitos. And I mean a lot of mosquitos. 100-200 mosquitos per cubic foot of air at night). So, I roll up the windows, turn on the AC on recirculate and when I do, mosquitos are expelled from the AC vents like a swarm of locusts to suck the occupants of the vehicle of blood like an infestation of vampires. I feel like I'm driving a vehicle designed by Alfred Hitchcock and having George Carlin riding shotgun at the same time.

I was thinking of dropping the kick guard, dropping the blowing motor and seeing if I could dust off the debris but I suspect the design engineers did something to preclude this remedy as per "Gray's Law'"*

*Gray's Law: "Incompetence carried to a sufficiently advance level is absolutely indistinguishable from deliberate malice."

Welcome to the forum! You are an excellent candidate for a cabin filter retrofit. Once you cut open the case to install the door, you'll have access the core to clean it out. Above your head is an aspirator, a little fan that determines what the interior temperature is. If these get clogged or go bad, they send a faulty signal to the HVAC computer and a perfectly running AC will not operate correctly.
 

Gildan

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Welcome to the forum! You are an excellent candidate for a cabin filter retrofit. Once you cut open the case to install the door, you'll have access the core to clean it out. Above your head is an aspirator, a little fan that determines what the interior temperature is. If these get clogged or go bad, they send a faulty signal to the HVAC computer and a perfectly running AC will not operate correctly.

That's exactly what I was thinking! The aspirator(s) (one in front and one for the back) are also another possible issue. The one in the back started making a really nasty buzzing sound due to the bearings in the tiny little fan being crappy in design. Getting to it to replace it is going to be an issue. :D
 

swathdiver

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That's exactly what I was thinking! The aspirator(s) (one in front and one for the back) are also another possible issue. The one in the back started making a really nasty buzzing sound due to the bearings in the tiny little fan being crappy in design. Getting to it to replace it is going to be an issue. :D
There are videos on youtube on how to do it, they make it look easy peasy. Pop the screens and clean them out first, you never know.
 

Joseph Garcia

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Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.
You are already receiving great recommendations from the knowledgeable folks on this Forum.

I like your graphic description of the mosquitos swarming from the AC air vents. I know a few folks who I would like to invite into the truck, just before I switch the AC on. :893Chainsaw-Smilie-
 

Gildan

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There are videos on youtube on how to do it, they make it look easy peasy. Pop the screens and clean them out first, you never know.
Tried that, doesn't work, can't get to the rear aspirator without disassembling the entire vehicle.

Had the whole system check and nothing can be found wrong with the system. The evaporator in the heater box is absolutely pristine clean. There are no error codes, the air mix doors are fine, refrigerant levels and pressures exactly to specs. Still the same problem, only worse today:

The system will cool the air properly *IF* you have the blower fan set to the lowest settings. But when you bump the fan level up to about half speed or higher, the air warms up to outside temperature. The inside/outside mix door is operating perfectly. It is a total mystery.
 

Bigkevschopshop

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You can do a reset on the auto climate control by holding 2 buttons down.
It makes all the blend door actuators reset etc. Can be good for tuning and making sure they know their stops etc.

I know the aspirators in the headliner can cause things to read wrong etc. I cleaned one and it fixed the issues i had a few years back of just sub par cooling here and there not all the time.
 

swathdiver

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Tried that, doesn't work, can't get to the rear aspirator without disassembling the entire vehicle.

Had the whole system check and nothing can be found wrong with the system. The evaporator in the heater box is absolutely pristine clean. There are no error codes, the air mix doors are fine, refrigerant levels and pressures exactly to specs. Still the same problem, only worse today:

The system will cool the air properly *IF* you have the blower fan set to the lowest settings. But when you bump the fan level up to about half speed or higher, the air warms up to outside temperature. The inside/outside mix door is operating perfectly. It is a total mystery.
Do you have a bi-directional scan tool that can read the commanded and actual settings for the actuators and various temperatures? Know a friend with the same AC controller as you to swap them out?
 

Gildan

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Do you have a bi-directional scan tool that can read the commanded and actual settings for the actuators and various temperatures? Know a friend with the same AC controller as you to swap them out?
Did that. Replaced the AC controller after tearing the whole dashboard, etc., apart. All the actuators are working as they should.

You can do a reset on the auto climate control by holding 2 buttons down.
It makes all the blend door actuators reset etc. Can be good for tuning and making sure they know their stops etc.

I know the aspirators in the headliner can cause things to read wrong etc. I cleaned one and it fixed the issues i had a few years back of just sub par cooling here and there not all the time.
Did that too. Reset the climate control. Did nothing. Replaced both aspirators in the head liner and nothing. Still does the same exact thing.

I measured the temperature of the evaporator in the hvac box, and it was clean and at the proper temperature. Still does the same exact thing.

We evacuated the system and there is no refrigerant loss whatsoever even after 6 months. Clutch on the compressor is fine, the compressor is fine, everything is fine and working, every single part is in perfect specs. I have literally spent a couple thousand dollars on diagnostics at two dealerships and two mechanics who specialize in AC systems and they are just scratching their head and say they've never seen anything like it before (which is a lie on their parts because this is a common problem with the 2008 from what I have found out).

So, we got everything back together and did an experiment. The only time you can actually get anything resembling cool air coming out of the vents is if you turn the fan to the lowest setting, lowest temperature setting, auxiliary back passenger AC on and recirculate on. The air coming out of the vents at that point goes down to about 55 to 60 degrees F. Turn the fan up even the slightest and their air out of the vents goes immediately up to outside temperature.

The high pressure port is at the proper pressures as is the low pressure ports. By all means and ways, the system should be performing perfectly, but is not. Turn the fan up just one tiny bit from the lowest setting and boom, the air out the vents is outside ambient temperature. No one can figure out the connection between fans speed on manual settings and why the temperature goes right to ambient outside temperature within 10 seconds of turning up the fan. I am literally at my wit's end over this incessant AC issue.

And now I know why the GMC dealerships want $2000 just to dust off the evaporator fins. Because it is a real you-know what to get to.
 

swathdiver

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Did that. Replaced the AC controller after tearing the whole dashboard, etc., apart. All the actuators are working as they should.


Did that too. Reset the climate control. Did nothing. Replaced both aspirators in the head liner and nothing. Still does the same exact thing.

I measured the temperature of the evaporator in the hvac box, and it was clean and at the proper temperature. Still does the same exact thing.

We evacuated the system and there is no refrigerant loss whatsoever even after 6 months. Clutch on the compressor is fine, the compressor is fine, everything is fine and working, every single part is in perfect specs. I have literally spent a couple thousand dollars on diagnostics at two dealerships and two mechanics who specialize in AC systems and they are just scratching their head and say they've never seen anything like it before (which is a lie on their parts because this is a common problem with the 2008 from what I have found out).

So, we got everything back together and did an experiment. The only time you can actually get anything resembling cool air coming out of the vents is if you turn the fan to the lowest setting, lowest temperature setting, auxiliary back passenger AC on and recirculate on. The air coming out of the vents at that point goes down to about 55 to 60 degrees F. Turn the fan up even the slightest and their air out of the vents goes immediately up to outside temperature.

The high pressure port is at the proper pressures as is the low pressure ports. By all means and ways, the system should be performing perfectly, but is not. Turn the fan up just one tiny bit from the lowest setting and boom, the air out the vents is outside ambient temperature. No one can figure out the connection between fans speed on manual settings and why the temperature goes right to ambient outside temperature within 10 seconds of turning up the fan. I am literally at my wit's end over this incessant AC issue.

And now I know why the GMC dealerships want $2000 just to dust off the evaporator fins. Because it is a real you-know what to get to.
Did you program the new AC controller to your vehicle?

What do you see on the Tech-2 with regards to the commanded and actual temperatures and door positions as you change the fan speeds?

Have you verified the condition of both cooling fans and the operation of all three relays? I had a car once that would overheat the motor and not cool the cabin unless the rear AC was on, even low and all was well.
 

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