# HVAC/Climate Control BCM Glitch



## revjpeterson (Oct 2, 2013)

Since someone might ask, the guy on the FB group had an LTZ, and mine is a Diesel, (both 2014) so this seems to cover both the automatic and the manual HVAC controls.


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## ChevyGuy (Dec 13, 2014)

revjpeterson said:


> When I restarted the engine, all of the HVAC commands I had given prior to shutting off the ignition quickly flashed across the MyLink screen in a matter of 5 seconds, and everything worked fine.


Interesting. So the controls "saw" your input, but was waiting on something else. I wonder what it was waiting for? (And it remembered your commands even though you powered everything off.)


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## ChevyMgr (Oct 27, 2010)

ChevyGuy said:


> Interesting. So the controls "saw" your input, but was waiting on something else. I wonder what it was waiting for? (And it remembered your commands even though you powered everything off.)


My Malibu locked up the OnStar Module and I hit buttons and tried to dial with Bluetooth for 5 minutes. When it unlocked itself every command I had done occurred and I couldn't get Ms Bluetooth to STFU for a few minutes. It dialed my home number at least 10 times. Funny to say the least.

Also the HVAC controller is a programmable module so it could be IT that locked up. Excuse me for using Brian's IT. Not sure if it is copyrighted.


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## Jim Frye (Mar 16, 2011)

It would be nice if these automotive OSs would throw some sort of error message (even BSOD) when they crashed. I guess they are too rudimentary to do that sort of thing. When all else fails, REBOOT!


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## MilTownSHO (Oct 9, 2013)

Mine has done the same thing. Hot summer night and we piled in the Cruze to go to the county fair, turned on the A/C and nothing. Restarted the car and it worked perfect.


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## KENSTV123 (Sep 21, 2014)

Sounds like the HVAC module halted on a command and just ran in a loop un-able to execute the further commands in cache, shutdown of the system restarts the whole processor loop and gets past the lockup, could be code glitch-buggy code or possibly some other module requesting data--like the bus master BCM, also could have been momentary erroneous data out of one of the sensors on the HVAC system--actuators, temp etc., I'm sure the door sensors in the HVAC system are not going to be industrial quality and a piece of dust or lint could easily cause a problem


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## CruzeTech (Mar 23, 2012)

This has happened to me before, as well. I realized it wasn't cooking sitting at the stop light after leaving my house, about a mile back. I turned off the car at the light and opened the door. Turned the car back on, and everything worked fine. Its only happened once in 52,000 miles, at least.


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## johnsluk (May 22, 2021)

revjpeterson said:


> What Happened: On a 10 mile drive home after getting groceries, I had gotten into a sun-warmed car, turned on the A/C as I drove away, but 4 miles into the drive, I noticed that the vehicle was not cooling, and it felt like just regular outside air coming through the vents. I tried using the AC switch and the outside air/recirculate switch, but nothing happened when I pressed either. I could change fan speeds and vent selection, but I noticed that nothing displayed on my MyLink screen when I did so, like any HVAC changes typically do. In the past, I have seen intermittent problems come and go from an engine restart, so I decided to pull over, shut down the car (including opening the door and removing the key to kill the retained accessory power and put the BCM to sleep), and see what happens. When I restarted the engine, all of the HVAC commands I had given prior to shutting off the ignition quickly flashed across the MyLink screen in a matter of 5 seconds, and everything worked fine.


Did you ever find the cause with this? Its now happening to my 2016 Z Series and would love to find a solution now that we are in summer here (Australia).


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