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Hey guys, I drive a 2010 Tahoe at work. I noted that as soon as the temperature reading on the DIC reads +2 Celscius (36 F) the A/C shuts off. You can't turn it back on by pushing the button. The light just flashes a couple of times and that's it. I took it to the dealer and they said that was normal operation to prevent the system from freezing. The other day I was driving and the temp. was +3 celsius. I had my dog in the truck and it was wet and snowing. As soon as then temp. dropped to +2 Celsius the windows fogged up in about 15 seconds. I had to pull over and wait for them to clear. It was painfully slow and they never completely clear up. The window has a rim of fog around it and the side windows are fogged up. It didnt do this in my 2004 Sierra as the A/C would stay turned on no matter what temperature and keep the windows clear. The A/C drys out the humidity in the air and keeps the condensation from forming on the windows. It's really a pain. Its been into the shop twice now with the same complaint and they tell me it's normal. I have tried rolling down the rear windows, all the windows, turning on the defrost on high - everything. I dont know how they expect it to clear when you have a truck full of people. I will try to find the TSB regarding this and post it.

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You can obtain the same result by cracking both front windows and turning up theheat to the front windshield full blast until clear or have your passengers alternate holding thier breaths until clear. zoz

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Negative. Nothing has worked. Had a 300 mile trip with the family yesterday, ice on the inside the whole trip. Windshield is fine, but the side windows ice over. 5 of us in there, lots of humidity in our exhaled air, but I have never had this issue before.

 

My understanding is the that AC will remove moisture from the air, but this won't come under under 40 degrees F...not sure what to do. Dealer said "yeah, they all do that" when I brought it in for tires. I didn't push it, but will when I need to go in again for something.

Not sure how GM manages the issues but know from 25 yrs of working with commercial tour buses that cold weather HVAC has it's quirks. Try keeping the windows clear for 50+ passengers. The big mechanical problem with gas refrigerant systems is compressor failures from "fluid slugs" at temps below @ 40 degrees. Some component manufacturers will void warranties if HVAC control systems don't prevent fluid slugging.

 

Most commercial tour buses deal with this issue using 2 methods:

1). Thermal-pane or 1/2 inch Lexan windows to insulate the temperature difference to minimize condensation on the glass. Practical on a $450K bus, not practical on a $30K truck.

2). The better coach designs have switchable ram air systems to force very cold outside fresh air into the HVAC system to naturally dehumidify without using the compressor. Normally this recirculation loop is closed...the evap core chills the recirc air to just above freezing (@ 35 degrees) where the moisture drops out. Then, rewarms the air (heater core) to room temp before forcing back into the cabin ducting and out directly on the side windows. Even with this design and the massive amounts of air they move, single pane glass will fogg & frost below @ 25 degrees if the coach is moving anywhere near cruising speeds. There is simply too much glass area, temperature differential, and contrary to what some say windchill does have an effect on inanimate objects.

 

The important things to remember to minimize this problem is to remove as much moisture from the interior as possible. A major contributor...snowy shoes...large amounts of moisure will get trapped in carpeted floors & floor mats, use rubber mats. As someone else remarked, draw as much outside air into the vehicle as possible. There is no way this small vehicle HVAC system will criculate the volumes of air as a bus so cracking open a window/sunroof will help outside air work through the HVAC system and through the vehicle.

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  • 3 weeks later...
I have a 2010 gmt 900 with just under 10k miles and its doing the exact same thing. Work as a gm tech and plan on taking the truck in to the dealer to have it checked out cause it can't be normal. Going to do a bulletin search tomorrow for this at work.

 

Just wondering if anyone has found anything out as far as a TSB goes?

Last couple of days have been in the -25C range and even with my truck

in a heated garage (humidity below 30%), one person in the truck the windows

all start to ice/fog up on the inside within minutes. No moisture, melted snow

in the truck, just a ticked driver.

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Well just got back from the dealership and they told me mine was the second one they have done.

So next time it gets really cold... we will see.

 

 

Thanks. My 2011 does it also and I thought it was me not pressing the tiny buttons correctly (I did read the manual btw). Next trip to the dealer I will have the do the TSB...

 

Thanks,

- Brad D -

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Has anyone seen any TSB results yet? I drive 20 kms to work and about 1/2 way there the ice starts taking over the windows. I've got lots of heat and defrost blower action going, just no defrosting going on. Taking my icebox in on Friday to get it checked and would like to have a positive note when I quiz them.

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Has anyone seen any TSB results yet? I drive 20 kms to work and about 1/2 way there the ice starts taking over the windows. I've got lots of heat and defrost blower action going, just no defrosting going on. Taking my icebox in on Friday to get it checked and would like to have a positive note when I quiz them.

 

 

So far so good, mine seems to be OK... so far.

Take this in and give it to them they will know what to do

 

 

Subject: Excessive Cabin Moisture/Reduced Window Clearing

Models:

2010-2011 Chevrolet Avalanche, Silverado, Suburban, Tahoe

2010-2011 GMC Sierra, Yukon, Yukon XL

With RPO C67 or CJ3

Manual Hvac System

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

CONDITION/CONCERN:

In rare cases, some customers may comment of excessive cabin moisture or difficulty keeping the

windows clear in low ambient temperatures.

RECOMMENDATION/INSTRUCTIONS:

If normal diagnostics do not lead to a correction, inspect the HVAC recirculation door by lowering the

glove box. The door should be in the "Fresh Air" position, which closes off the recirculation opening

behind the glove box when the HVAC controls are in the floor to defrost position. If not, then follow

the procedure below:

1. Turn the vehicle ON.

2. Set the HVAC controls to a Vent/Panel position.

3. Press the Recirculation button on the control head.

4. Move the HVAC controls back to a Floor / Defrost position

5. Verify the Recirculation door has moved to the Fresh Air position by visual inspection.

6. Return the vehicle back to the owner and instruction them NOT to use the recirculation button and

that Engineering is working on a software update.

7. If the vehicle returns with this concern and the recirculation door is again in the recirculation

position then Contact GM Technical Assistance.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition

exhibited is resolved without completing every step, the remaining steps do not need to be

performed.

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