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Well egg on my face. I just bought 3 weeks ago a new 2017 Colorado LT CCLB and since I purchased it I have had problems. First it was the dreaded "Exhaust Fluid Poor Quality" warning which the dealer seems to have fixed. The jury is still out regarding that one. Last week the AC started freezing up on a trip to the lake. Outside temps were in the 90's and high humidity. The lines were covered with 1/8" of ice. Took it to the dealer and they said the system controls had to be reprogrammed (per GM). This week we drove up to Detroit and again it froze up. Called the dealer from the road and he said bring it back in.


I have since been doing a lot of research on this forum and others. There seems to be a lot of owners of Gen 2 Colorado/Canyon trucks that are having this same issue. There evidently is a design flaw with this system. Turning the AC compressor on and off for long intervals so that the system can thaw out is not a fix in my opinion.


Several years ago I told myself and anyone within earshot that I would NEVER purchase a new GM product again. Well I did and now I have egg on my face. I guess I will just have to make GM buy back this one like they did the last.


Does anyone know of a permanent fix for this problem and please don't tell me cycling the compressor for long intervals is the fix. I really do like the truck for the most part.
 

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Well egg on my face. I just bought 3 weeks ago a new 2017 Colorado LT CCLB and since I purchased it I have had problems. First it was the dreaded "Exhaust Fluid Poor Quality" warning which the dealer seems to have fixed. The jury is still out regarding that one. Last week the AC started freezing up on a trip to the lake. Outside temps were in the 90's and high humidity. The lines were covered with 1/8" of ice. Took it to the dealer and they said the system controls had to be reprogrammed (per GM). This week we drove up to Detroit and again it froze up. Called the dealer from the road and he said bring it back in.


I have since been doing a lot of research on this forum and others. There seems to be a lot of owners of Gen 2 Colorado/Canyon trucks that are having this same issue. There evidently is a design flaw with this system. Turning the AC compressor on and off for long intervals so that the system can thaw out is not a fix in my opinion.


Several years ago I told myself and anyone within earshot that I would NEVER purchase a new GM product again. Well I did and now I have egg on my face. I guess I will just have to make GM buy back this one like they did the last.


Does anyone know of a permanent fix for this problem and please don't tell me cycling the compressor for long intervals is the fix. I really do like the truck for the most part.
Not sure where you get the "lot of owners" with the problem of the AC freezing over. There have been a few. There have been some other issues with the HVAC on the early units, your 2017 would not be experiencing the flapper door failure.

Doesn't sound like you will be happy with this truck, I would dump it as quick as possible. Life is too short to drive a truck you don't trust or like.
 

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My AC froze up one time...it was hot and humid and I was leaving for a 200 mile road trip. I had it on the lowest setting with the recirculation button pressed. Once it had set for a few hours it started working again. I can say I stopped using the recirculation button after that. Not using it may take an extra minute or two to cool the car down, but it still gets cold pretty quick and has not frozen up again.
 

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I have spent several evenings reading posts, some of them on this forum, from people with the exact same problem as I am experiencing. That is why I said "lot of owners". If I read more than 20 posts I consider that many. I factor in those people that overlook issues like these because they are willing to live with it.

I worked for a company whose major customers were the auto industry. If we built a machine for them and it didn't work 100% then we stuck with them until the issues were fixed. Not because we had to but because we built our reputation as the best in business because of our service. And we were building "one off" machines not cookie cutter units like automobiles. GM has used the general public as their R&D departments for too many years. GM was also the worst customer we had. They would beat us to death trying to get the best price and then after we were awarded the contract they would make numerous changes and refuse to pay for them. They were a bunch of whiney, spoiled, arrogant. Don't get me started!! They need to step up when they make a mistake and fix it. I consider this AC problem as a design flaw.

And by the way I never use the recirculation button to cool the car. I like fresh air.
 

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Like BeastStar mentioned, when it freezes up do you have it on Recirc? I know our Jeep says to run AC in recirc only for the first few minutes after that put it to normal as it may cause the unit to freeze up.

If it is low on freon it can freeze up too

My Canyon has never froze up, but the only time I put it in recirc is when I am near a diesel or driving by the slaughter house
 

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Welcome to the forum.
Sorry to hear about your A/C experience. As I live in FL, this is a too important a function to have take a dump on us. I currently own my 2nd and 3rd (17's) 2nd Gen Colorado's, and along with my 1st(15), I've haven't experienced any A/C issues to date.
Since this truck 3 wks old, I would take it the dealer and have the issue/complaint on record, and possibly even....fixed.

As far as dealing with a Mfg goes, that experience is nothing unique. They all pull the same ****, as that is what purchasers are paid to do, regardless of industry. If they're bitching and moaning at you, it means somebody else didn't beat your price or couldn't make their needed item. If they are not, they are making a ton of profit, or somebody came up with a better machine.
 

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There is a "notification", from GM, to the dealer's service departments regarding exactly this issue. I'll see if I can find it.
 

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Well egg on my face. I just bought 3 weeks ago a new 2017 Colorado LT CCLB and since I purchased it I have had problems. First it was the dreaded "Exhaust Fluid Poor Quality" warning which the dealer seems to have fixed. The jury is still out regarding that one. Last week the AC started freezing up on a trip to the lake. Outside temps were in the 90's and high humidity. The lines were covered with 1/8" of ice. Took it to the dealer and they said the system controls had to be reprogrammed (per GM). This week we drove up to Detroit and again it froze up. Called the dealer from the road and he said bring it back in.


I have since been doing a lot of research on this forum and others. There seems to be a lot of owners of Gen 2 Colorado/Canyon trucks that are having this same issue. There evidently is a design flaw with this system. Turning the AC compressor on and off for long intervals so that the system can thaw out is not a fix in my opinion.


Several years ago I told myself and anyone within earshot that I would NEVER purchase a new GM product again. Well I did and now I have egg on my face. I guess I will just have to make GM buy back this one like they did the last.


Does anyone know of a permanent fix for this problem and please don't tell me cycling the compressor for long intervals is the fix. I really do like the truck for the most part.
Just to be sure, when you say freeze up you mean the evap freezes and it wont blow any air? Or it blows hot air?
 

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Discussion Starter #10
When I say freezes up I am referring to the fact that the low pressure line going to the evaporator coil has about 3/16" to 1/4" of ice on it so I would assume the evaporator coil is iced up also. The air that comes out of the vents is slightly cool and somewhat less volume. If I turn the AC switch off and wait a few minutes and turn it back on then the air is cold again. This problem first occurred last week after about 2 hours of expressway driving. The outside temperature was approximately 90 deg. F and very high humidity approx. 75%. I took it to the dealer and they consulted with GM and they said to install a new program for the control. This program was to cycle the AC compressor in intervals that would eliminate the freezing. After they did the reprogram I noticed that there was a large swing in the temperature of the air coming out of the vents. I did not have a thermometer to check the actual temperature. Yesterday I was coming back from Detroit to Cincinnati and after about 3 hours of driving the same thing happened. I pulled off an exit and opened the hood and again the lines were crusted with ice.


I am new to this forum but am a member of several auto related forums. I am a retired sales engineer and spent many years in machine design and electrical design. I have very little HVAC experience but I know how these systems are supposed to work. I have bought in excess of 20 new automobiles in my life and never had one that the AC didn't work perfectly in. I guess GM has found a new way of disappointing me. I gave them a second chance because of the rave reviews on this truck and specifically the baby Duramaxx.


I have gotten GM directly involved with this issue and Friday we are taking it to the dealer for repeat service. If it is not fixed correctly this time then GM will be sending a tech to look at it.
 

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I've owned my used 2016 Colorado for about 3-4 weeks, so not a ton of drive time, but I do live in Charleston, SC where it's terribly hot and humid over the summers and had one 2 hour trip to Hilton Head so far. I've found myself turning the temp up to 74-75 to keep from freezing myself. A/C seems to be great so far. I will say, my experience with pipes freezing, at least when it comes to homes, has been from a blockage of airflow somewhere, typically when someone hasn't changed their filter in a long time so it's gotten pretty caked up. Not sure where in the car HVAC system a similar block would be occurring, but I don't think a reprogram is going to fix that. I was not aware of the need to change from recirculation to fresh after start up. I always stay on recirc because it seems more efficient than pulling in that hot air, but I'll have to read up on that more.
 

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When I say freezes up I am referring to the fact that the low pressure line going to the evaporator coil has about 3/16" to 1/4" of ice on it so I would assume the evaporator coil is iced up also. The air that comes out of the vents is slightly cool and somewhat less volume. If I turn the AC switch off and wait a few minutes and turn it back on then the air is cold again. This problem first occurred last week after about 2 hours of expressway driving. The outside temperature was approximately 90 deg. F and very high humidity approx. 75%. I took it to the dealer and they consulted with GM and they said to install a new program for the control. This program was to cycle the AC compressor in intervals that would eliminate the freezing. After they did the reprogram I noticed that there was a large swing in the temperature of the air coming out of the vents. I did not have a thermometer to check the actual temperature. Yesterday I was coming back from Detroit to Cincinnati and after about 3 hours of driving the same thing happened. I pulled off an exit and opened the hood and again the lines were crusted with ice.


I am new to this forum but am a member of several auto related forums. I am a retired sales engineer and spent many years in machine design and electrical design. I have very little HVAC experience but I know how these systems are supposed to work. I have bought in excess of 20 new automobiles in my life and never had one that the AC didn't work perfectly in. I guess GM has found a new way of disappointing me. I gave them a second chance because of the rave reviews on this truck and specifically the baby Duramaxx.


I have gotten GM directly involved with this issue and Friday we are taking it to the dealer for repeat service. If it is not fixed correctly this time then GM will be sending a tech to look at it.
gotcha, that is a crappy way to "fix" it. Cycle the compressor basically randomly to let it thaw out, silly. Where I live it never gets that humid so I doubt I will ever see that problem. If they have a "fix" by re-programming the BCM to do that silly cycling seems like there must be a large complaint?? What they really need is a good old temp cycling switch on the evap to shut it down when it really needs it. That aint going to happen though, have to design something like that into the system. I wonder if they checked other things like freon amount and pressure switches before giving it the ol' "can't get my hands dirty reprogram"??? lazy dorks.....anyway, good luck....


update: according to the elect manual it does have an evap temp sensor, maybe they should check that....

from the manual-------

Evaporator Temperature Sensor:
The evaporator temperature sensor is a 2-wire negative temperature coefficient thermistor. The sensor operates within a temperature range of −40 to +85°C (−40 to +185°F). The sensor is installed at the evaporator and measures its temperature. If the temperature drops under 3°C (38°F), the compressor will be switched off in order to prevent a frozen evaporator.
 

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That is exactly what is failing or being ignored by the computer in your truck. The evap temperature sensor is what is suppose to shut down the compressor prior to the evaporator reaching the freezing point. A good automotive AC tech would know this.

A work around for this is to add a little R-134 to the system so the expansion temperature point is a little above freezing. I would not do this because yours is new and under warranty. So let them fix it.

In 1st gen 2004 and 2005 Colorados trucks we had the opposite problem. The expansion temp sensor was triggering at around 46 F. which was too high. To fix the problem GM came out with a new temp sensor that triggered at a lower temperature. Unfortunately you had to pull the dash apart to get the evaporator out and replace the sensor. So what we did on out of warranty trucks was to externally add a resistor across the sensor to lower the trigger point. It worked great and mine still has it installed 12 years later.

I'm not suggesting that you modify a new under warranty truck.

Running in recirculate also will delay the accumulation of ice. This will not fix your problem but it will reduce it's number of occurrences.

Good luck. This is just basic Automotive AC design and operation. GM can fix it if you get someone other than an error code reader mechanic.
 

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That is exactly what is failing or being ignored by the computer in your truck. The evap temperature sensor is what is suppose to shut down the compressor prior to the evaporator reaching the freezing point. A good automotive AC tech would know this.

A work around for this is to add a little R-134 to the system so the expansion temperature point is a little above freezing. I would not do this because yours is new and under warranty. So let them fix it.

In 1st gen 2004 and 2005 Colorados trucks we had the opposite problem. The expansion temp sensor was triggering at around 46 F. which was too high. To fix the problem GM came out with a new temp sensor that triggered at a lower temperature. Unfortunately you had to pull the dash apart to get the evaporator out and replace the sensor. So what we did on out of warranty trucks was to externally add a resistor across the sensor to lower the trigger point. It worked great and mine still has it installed 12 years later.

I'm not suggesting that you modify a new under warranty truck.

Running in recirculate also will delay the accumulation of ice. This will not fix your problem but it will reduce it's number of occurrences.

Good luck. This is just basic Automotive AC design and operation. GM can fix it if you get someone other than an error code reader mechanic.
And this my friends should get the post of the month award! Well done sir. :) LOL maybe I should just hit the "like" button?

p.s. running in recirc mode seems like it would be a two edged sword. On and you get dry but cold air, off and you get hot but humid air. pick you poison for freezing conditions I guess.... A slow fan speed would make it freeze faster too.

On the 1st gen trucks you could add a resistor to make the ECM think the evap was hotter? Wouldn't work in this case because you cant un-add resistance to make it think it's colder ;) Unless of course you put a resistor in parallel with the thrmistor, but then there is that pesky rip the whole dash out to get to it thing...Oh wait, how about in the line between the thermister and ECM to ground? Sorry, was getting my nerd on.
:nerd:
 

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That is exactly what is failing or being ignored by the computer in your truck. The evap temperature sensor is what is suppose to shut down the compressor prior to the evaporator reaching the freezing point. A good automotive AC tech would know this.
My question is - Why is the system letting the evaporator get this cold in the first place? The system has two sensors which seem to be backup sensors for when other controls fail. This is one of them, and the other is a high pressure sensor. But you have multiple first line sensors - an outside air sensor, a sun load sensor, a cabin temp sensor, and, I believe, a vent sensor or two. Why isn't all this feedback system (particularly the vent sensor) working to keep temps in a more reasonable range in the first place?

I suspect this is the common problem effecting all or most of the A/C complaints we see here.

When I take my Service Manager (who used to be an A/C tech himself) for a ride in my truck, he tells me that the temp is controlled by the temperature door doing crude swings from one extreme to the other (my paraphrasing). I'm sorry, but the idea of GM designing such a crude system, in the day of digital controls and actuators, doesn't pass my reasonableness filter. I've looked all over the service manual for a theory of operation which describes the logic of the system, but there is none. There is not even a routine for troubleshooting inconsistent vent temperatures, all it says is to call the internal tech line.

But with a variable compressor, supposedly coupled to at least a pair of interior sensors and operating through a variable door, I can't believe that the system is designed to act worse than all the primitive systems which preceeded it. I think the dealers are unwilling to call the tech line. Perhaps they are penalized for doing so, similar to the other goofy management incentives we know GM to use relative to dealer service.
 

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My question is - Why is the system letting the evaporator get this cold in the first place? The system has two sensors which seem to be backup sensors for when other controls fail. This is one of them, and the other is a high pressure sensor. But you have multiple first line sensors - an outside air sensor, a sun load sensor, a cabin temp sensor, and, I believe, a vent sensor or two. Why isn't all this feedback system (particularly the vent sensor) working to keep temps in a more reasonable range in the first place?

I suspect this is the common problem effecting all or most of the A/C complaints we see here.

When I take my Service Manager (who used to be an A/C tech himself) for a ride in my truck, he tells me that the temp is controlled by the temperature door doing crude swings from one extreme to the other (my paraphrasing). I'm sorry, but the idea of GM designing such a crude system, in the day of digital controls and actuators, doesn't pass my reasonableness filter. I've looked all over the service manual for a theory of operation which describes the logic of the system, but there is none. There is not even a routine for troubleshooting inconsistent vent temperatures, all it says is to call the internal tech line.

But with a variable compressor, supposedly coupled to at least a pair of interior sensors and operating through a variable door, I can't believe that the system is designed to act worse than all the primitive systems which preceeded it. I think the dealers are unwilling to call the tech line. Perhaps they are penalized for doing so, similar to the other goofy management incentives we know GM to use relative to dealer service.
Well the system is still basically the same since the beginning of AC. Some of those sensors I do believe are gong to be only on an auto system(like the cabin temp and sun load) The compressor is either on or off so the evap is either cold or not. So, it needs a door to regulate temp.(vent temp not evap temp) Why in the world the evap temp and pressure sensors aren't working to keep it in the cold but not frozen state is anyone's guess, well, actually a tech's job to figure out (its broken). Not too long ago GM used a fixed orifice and low pressure sensor to cycle the compressor and it worked perfectly. No computer needed. Go figure right?
 

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I myself have noticed the inconsistency with the AC. The worst part is I cannot duplicate it so I am out on the dealer doing anything to fix it.
 

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The compressor is either on or off so the evap is either cold or not. So, it needs a door to regulate temp.(vent temp not evap temp) ....Not too long ago GM used a fixed orifice and low pressure sensor to cycle the compressor and it worked perfectly. No computer needed. Go figure right?
My understanding is that it has a variable displacement compressor, meaning temperature regulation should be even more easily achieved. And I don't have any problem with the idea of a temp door, per se, but I do have a problem with the system not seeming to have any predictive logic and only being able to regulate by overshooting in one direction and then compensating by overshooting in the other.
 

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When you compare a modern vehicle AC system to one in your home you will see that you have a much more complex system in a vehicle. This is because it has to operate well within a WIDE range of variables. Some of these are the variable flow of air across the evaporator (fan speed), the variable rate of flow of air over the condenser (vehicle speed and radiator fan speed), the variable speed of the compressor (controlled by engine speed) and wide variable exposure to sunlight and shade (solar radiation).

For comfort we not only try to control the air temperature but also the humidity with the AC system. Right now it is 76 degrees F in my house and 30% humidity. It is 75 degrees and 93% humidity outside. Outside is uncomfortable while inside is right where I like it. We expect a vehicle AC system to operate well at 115F and 15% humidity in the desert or 85F and 95% humidity in the midwest or south. Humidity control is a big thing when making people feel comfortable.

So in a vehicle we build an over capacity system and then put limit sensors on it to control it's operation under most environmental variables. The main method of control is compressor off and on cycles and cabin air flow. In years past we use to tun the compressor all of the time and mix the cold air with non- cooled air using a blend door. Most systems today do not do this for fuel efficiency.

So there are sensors on the system and vehicle to tell a computer what is happening. The computer decides when to turn off and on the compressor for efficient operation while keeping the people in comfort. The evap temperature sensor's prime mission is to keep the evaporator running at slightly above freezing. At this point we get the maximum possible cooling and moisture removal when necessary. Not all vehicles have one. If they do not, then the system has to be designed with a higher static pressure (more refrigerant) to prevent freeze up. This why I stated in a previous posting that you could add a little R-134 to the system and fix or mask over your problem. This is how it is normally done in a home system.

I am not suggesting that you do this. Make GM fix their sensor problem.



So
 

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My understanding is that it has a variable displacement compressor, meaning temperature regulation should be even more easily achieved. And I don't have any problem with the idea of a temp door, per se, but I do have a problem with the system not seeming to have any predictive logic and only being able to regulate by overshooting in one direction and then compensating by overshooting in the other.
could be, not sure. I just saw the 2015 manual has a switch to turn off the compressor when it gets too cold. I don't have access to a 16 or 17 manual.

I can't imagine the system is designed to overshoot like you say. Must be something broken, right?
 
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