2nd post was a repeat with more info.

 

Does your recharge can have a gauge on it? If so it should indicate if the system is low.

 

The situation has been that maybe twice per year, after the car is driven an hour or so and sits for somewhere around 4 hours, when you start the car up, the A/C comes on. After 5 through 10 minutes it will turn off. Pushing the control button yields three flashes of the Amber LED and then the unit goes back off again. No cold air. Will stay that way all day no matter how long you leave it off or how many times you try. After it sits overnight, start up the next morning, same thing. After you drive at approximately 10 minutes compressor will kick on, light comes on and you have cold air. Can make all the short trips I want, stopping at gas stations, convenience stores, half an hour in the grocery store, etc. No issues.

Yesterday, the situation was similar. Drove the car for an hour, it sat 4 hours and then drove it home. A/C worked all the way there and worked for the first 10 minutes on the drive home, then no A/C. The only difference between this time and all of the others as that the light on the control stayed on. I did turn the AC control off and back on and the light came back on solid. Turn it off again, let it sit for 15 minutes, turned it on and same thing. Therefore, I thought it might be a different issue. Got up this morning and went to turn the unit on and the light flash three times and went off. Drove it 10 minutes and the damn thing came back on and it's blowing cold.

On this forum and in a couple of other places on the net I've seen several suggestions, the two most prevalent are you need to have a dealer reprogram the environmental control panel and the second one is there is a temperature sensor issue somewhere.

Open to any all suggestions, Diagnostics I should do or what you think it may be. Thanks as always!

 

Lets see if this shows up.

 

First thing is that I'm NOT a mechanic and secondly, I don't know crap about a/c. That being said, I'd check my grounds and fuses. It might possibly be corrosion on either one. If not that, then you'll have to get advice from someone who knows about these things. Like other members.

 

Please do not discuss the same issue in multiple threads. It becomes impossible to follow. I merged them, so you get what you get.

 

Existing TSB:There has been a factory service bulletin for that type of concern. Here is what it states.



.

• A/C - Indicators Flashing (Normal Condition)

Bulletin No.: 07-01-38-003

Date: June 12, 2007

INFORMATION
Subject:
Information for Vehicles with HVAC Control Module A/C And Recirculation Indicators Flashing Models:
2008 Buick Enclave
2007-2008 Cadillac Escalade Models
2006-2007 Chevrolet Monte Carlo
2006-2008 Chevrolet Impala
2007-2008 Chevrolet Avalanche, Equinox, Silverado, Suburban, Tahoe
2007-2008 GMC Acadia, Sierra, Yukon Models
2007-2008 Pontiac Torrent
2008 HUMMER H2
2007-2008 Saturn OUTLOOK
2008 Saturn VUE

Condition/Concern

Some customers may comment that the Air Conditioning (A/C) indicator on the Heating Ventilation and Air Conditioning (HVAC) Control Module flashes then turns off after they press the A/C button.
Others may comment that the Recirculation indicator on the HVAC Control Module flashes then turns off after they press the Recirculation button.

This is normal operation for the HVAC Control Module and indicates that the A/C or Recirculation function is not available at this time.

Reasons that the A/C may not be available (calibrated values vary by program) are listed below. Consult the appropriate vehicle Service Information (SI) for detailed HVAC Description and Operation:

• Ambient Air Temperature is too low (if equipped with Ambient Air Temperature Sensor)
• Vehicle voltage less than 9.5 volts
• Refrigerant Pressure too low
• Refrigerant Pressure too high
• Engine Coolant Temperature too high
• Engine is not in RUN
• HVAC Control Head is in the OFF position

Reasons Recirculation may not be available: Mode switch in Floor, Defog or Defrost mode.

The reason(s) A/C is currently disabled can be viewed with a Tech 2(R) by navigating to HVAC Data display and viewing the "A/C Permission" parameter.

Recommendation/Instructions
Do not replace as this is normal operation.

----------
Since this vehicle has a BCM, it probably has stored codes related to this issue. In order to access these codes which do not turn on the service engine soon light, you need to connect a code scanner to the diagnostic port that can read and retrieve these codes. AutoZone will read service engine soon light codes but not body control module codes.

You simply need a more capable scanner to access these codes. You have the highest chance of diagnosing this when the system is acting up.

Keep in mind that the AC not being available May be for different reasons at different times. This seems probable based on the inconsistent behavior you seem to be seeing.

This is one of the fastest ways to figure out what is going on. If you have a mechanic do a diagnostic, it usually costs 1 hour of Labor. If you choose to do so, make sure you get a copy of the actual codes not what they say the codes mean. You can post them here and we will try to sort it out.

 

TY Derf. Apologies. The reason I did so is the second post had additional information that happened the next day. Since the moderators had not approved or posted my first post yet, I hope they might see that the second was a dupe and just delete the first.

 

Thank you so much! I do have a decent code reader, at least for a I occasionally fix stuff) DIYer like myself, the Autec ML629 (ABS, SRS, Engine, Transmission). Probably does not do BCM though I haven't looked. I appreciate the service bulletin. If I look at the conditions listed, they really don't seem applicable. This has happened when the ambient air has been in the upper 70s and when it is in the mid-90s and all in between. For what it's worth, temp reading on the dash seems to be reporting correctly. Vehicle voltage was correct. Refrigerant pressure within range. Coolant temp was fine. I had checked all three after we used a couple of occasions.

As noted, this last time was a slight bit of an anomaly in that the A/C light stayed on as opposed to actually blinking three times and going off but the rest of the symptoms were exactly the same. Drove the car for an hour, parked for 4 hours, began driving home, air worked for 5 to 10 minutes and then went out. Would not come on again no matter what you do until the car sat overnight. Started the car in the morning, same situation. Drive car 10 to 15 minutes and the air comes on and the A/C light comes on.

Do you think the situation like this would throw a code stored in the BCM? If so, and I need someone to read a BCM code, would be best to take it to a GM stealer or do you think my well-equipped, well-known local automotive shop would be able to do so? Guessing whoever is going to want probably $150 just to take a few minutes to read the codes. The challenge is this happens only a couple of times per year. In order to take it somewhere and have someone take a look at what is actively going on, I would immediately have to be able to drive it to the shop when the situation occurs Historically, 100% of the time, once it sits overnight, when I start it and drive it 10 to 15 minutes, the air comes back on. It would take me longer than that to get to the shop so more than likely the situation would have self-corrected by then.

Any comments on the couple of things I've seen on this site and others that the fix seems to be either reprogramming the control panel or possibly finding and replacing a temp sensor which may be stored behind the grill or somewhere else?

I know I'm grasping at straws. Any and all insight and suggestions are greatly appreciated. Thanks so much for the reply so far!

 

If your reader can read ABS and SRS I'm confident it can read BCM codes as well. Plug it in and give it a try. It may have stored some of the codes.

As for the ultimate cause of the issue, there is no way for us to take it much further unless you can set up your scanner for real Time data capture or display, which you should be able to do.

The next thing that goes along with that is that you need to determine what AC related data you can access with the scanner. The idea being that you need to monitor say seven different data values and see which one acts up when this occurs.

What is the system pressure with the vehicle off on an 80° day?
What are the high and low side pressures on a 80° day with the AC running normally?

I suspect if you take this in, if there are no clear codes that point to anything, a dealership will be happy to start swapping high pressure low pressure switches and other things at your expense. When that doesn't work, then they will recommend a reprogram. When that doesn't work, they will recommend you go to an AC specialist. You'll be out $500 and no closer to solving the mystery.

The three blinks mean the system is unavailable. Whole host of reasons why that might be. If it is something that is happening constantly or frequently, it is much easier to troubleshoot. If it happens two days out of 365, you are not likely to find it other than leaving your real time data logger hooked up for an entire year to catch when it happens. You can throw parts at it and verify the system pressure.

If the reality of the situation is overwhelming, and you feel you must do something to try to address it, take it to a professional, have them check the AC system. If they do not find any codes and you do not find any codes, and the pressures are within spec, I would guess the most likely part to act up and cause this available not available available behavior would be the high pressure low pressure cutoff switch. I say this because it is the one component in the system that can completely shut it down. If it is a combination switch, it can do this in both directions if it is defective in both directions.
You will likely have to pay to have the existing refrigerant recovered from the system, the sensor replaced, and then the refrigerant put back. Part plus labor.

The above is a total guess.