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

[swathdiver]

Oh, let me summon some HVAC experts... @Doubeleive @91RS @gpracer1 @PlunkZ71 @Rward @Matthew Jeschke

 

[Doubeleive]

sounds fishy to me, like James said you need to look at commanded temp -vs-actual temp, and monitor it as you adjust it (in real time).
I would also scan the whole hvac system and look at any errors
you never said if a tech2 or similar capable tool was used or not
there are temperature sensors in the hvac tunnels about 6 or so all together, plus the 2 ambient roof sensors and the sun sensor in the center dash, those all work together. not sure if the outside ambient temp sensor affects the hvac or not.
if the ac main control was replaced you need to be sure it has the correct calibration for your vehicle, this can be done with the tech2 and acdelco tds web
also just because a actuator motor moves all the way open to shut does not mean it works properly, they can get goofey which is why you need to monitor the temps and if necessary visually watch the actuator at the same time.

 

[alpha_omega]

Yes. The outside ambient air sensor does play a roll, as do the grounds for whatever reason. If you haven’t already, check and clean all of your ground to body points (clean and check for tightness on all of ring crimp connections and clean the body where it mounts).

I third the notion of a Tech2 or similar scan tool. You answered most all of the questions that I had regarding the compressor, clutch, interior sensors and the control units.
Did the 2008’s have a digital control in the dash, or was it the knob and dials? If I remember correctly they were digital correct?

I know that you have power to the system, but did you check the blower resister/control module with a volt meter and with a scan tool? And did you say that both the high and low sides were checked and all was good or did they just check the high side?

Does your compressor turn on when you have a mode selected (other than low) when it is not blowing cold air? If the compressor turns off or doesn’t come on when you switch over to another setting above low, that will help narrow things down a bit.

 

[alpha_omega]

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 ). 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."

Try this tool out on your fins, and you might consider straightening any that are bent. You can also use a condenser coil cleaner and a garden hose if you have any stubborn bugs or road grime that won’t come off.

I bought one of these a while back and the thing works beautifully. I use it on my Denali a couple times a year and my Deere a couple times a day when I’m mowing the pastures.

48″ Air Comb® Filter and Radiator Cleaner | Innovative Products of America

The IPA® 48″ Air Comb® is a new type of blow gun that cleans radiators, condensors, and air filters in just seconds.

www.ipatools.com

A couple other thoughts that I had:
Does your fan turn on? Does it stay on when you turn the switch to low or from low to another setting?

Have you checked ALL of the relays and fuses yourself (not gone by what the stealership says)?

Have you checked the compressor pressure switch (one on the compressor one on the radiator/condenser), the compressor solenoid and the gap for the compressor clutch pulley?

All of these questions can cause a malfunction and/or intermittent function. You may even get phantom “cold air” in low, but the compressor isn’t switching on, so when you go to Med, high, auto then it fully shuts down or stops blowing the cold air pressurized in the line.


Did you do a “factory reset”?
Steps:
-turn off the a/c,
-shut off the vehicle,
-disconnect positive + battery cable,
-wait for 10min (set your alarm),
-*Before reconnecting battery* touch the positive lead + to the negative terminal lead (this discharges the system similar to a capacitor),
-reconnect positive lead to the battery,
-start the vehicle *waiting 5min before turning on the a/c* (this is done so the other systems can cycle through their reset/relearn)

Hopefully I got all of that correct. I’m pretty sure Rocketman and some other guys have a thread or two out there as well or can correct me if I missed anything. Remember this is different than the “press two buttons at the same time” kind of reset.
There is one other dealership reset done with different buttons, but I can’t recall which ones they were. Auto and defrost?

 

[RED TAHOE LS]

unfortunately, the evaporater needs cleaned with a water hose. Remove glove box completely, remove blower motor, to the left is the evaporater core. GOOD TOOTHBRUSH to clean the fins. Then spray core with purple power (walmart) and let it soak while you remove anything in the bottom of the case. Use your floor mats and arrange to get the water flowing out of the door opening to the ground. use a good nozzle to make good pressure to wash out the core. It will try.....trust me. My 99 with 226k, cools specs 38-42.......JMHO

 

[petethepug]

NuBrite is the absolute best condenser & evap coil cleaner. It’ll actually get the evap fins back to shiny again. It was revolutionary when Calgon introduced it 20+ years ago because it foamed up and dissolved decades of grime that nothing else could ever remove.

In my commercial HVAC days I’d have a pair of shorts, face mask and dishwashers gloves to apply it to condenser coils on multi story roof tops. I’d spend an entire day applying it and right rinsing it off until air flow returned.

It’s available in retail now but in the confines of the truck have a 2x2 home window fan blowing air from drivers seat out the p/s door and aforementioned safety equipment on. Do overkill on protection to keep the product off ALL interior surfaces. It’s like bleach so watch the splatter. Do Not use trigger hose nozzle or the initial squeeze of the handle will make it splatter everywhere. Use a short twist style nozzle for control.

This stuff will also defunk any rank smells too.

Good Luck!