Auto HVAC turning on by itself???

[Mike534x]

Hey everyone! Having a bizarre issue with the Auto HVAC/Digital Climate controls. Driving to work this morning, the A/C turned on like I hit the button. Which is weird, so I turn it off and all is well for about 5 minutes. Again, sitting at a stop light (nothing is near, or touch the controls) the A/C yet again comes on. The compressor can be heard kicking in, and cold air is blowing from the vents. I'm going to do my best to describe this. So when you hit "Auto" it has the little arrow pointing to the driver that pops up on the display? When it comes on by itself, the arrow is pointing to the passenger side instead. I've never seen this before.

I've already replaced the blower control module 3 summers ago, after losing all fan speeds and had the infamous "burnt"/melted connector. So is it possible that module is acting up, or could this be an issue in the Auto HVAC panel itself? It did it going there, and again coming home from work.

 

[TJBaker57]

On my 2002 with RPO CJ2 if I press the Auto button repeatedly it cycles between driver side arrow and passenger side arrow.

Only once did my AC turn itself on. As with you I turned it off and shortly thereafter it turned itself on again. In my case though it happened during a security relearn on one of the ten minute wait cycles!!

 

[Mike534x]

Did you ever figure out what was the cause of yours coming back on? I was gonna try pulling the HVAC fuses and letting it sit overnight to see if that changes anything (aside from needing to do the blend door relearn).

 

[TJBaker57]

Did you ever figure out what was the cause of yours coming back on? I was gonna try pulling the HVAC fuses and letting it sit overnight to see if that changes anything (aside from needing to do the blend door relearn).

I might still have the serial data I recorded during the relearn. I think I looked it over then but I do not recall having come to any conclusion. I'm going to have another look at it.

 

[TJBaker57]

Did you ever figure out what was the cause of yours coming back on? I was gonna try pulling the HVAC fuses and letting it sit overnight to see if that changes anything (aside from needing to do the blend door relearn).

I just reviewed the data and I can see where out of the blue the fan announces it is activated. I can see where I turned it off then a minute or so later it again turns on. I left it on at that point. There was no request for the compressor or anything else, just the fan decided to turn on.

I have no guess why.

 

[Mike534x]

I just reviewed the data and I can see where out of the blue the fan announces it is activated. I can see where I turned it off then a minute or so later it again turns on. I left it on at that point. There was no request for the compressor or anything else, just the fan decided to turn on.

I have no guess why.

Interesting. The only thing different with mine, is that the compressor is actually kicking on when the system randomly turns itself on.

 

[budwich]

what "state" was the controller in? ie. was auto selected or otherwise or was it "officially" turned off with the OFF button.... or are you just hitting the "*" (AC function) to turn things "off". IF the thing wasn't turned OFF, then I do believe there are still "live functions" that will happen depending on sensor "levels" and settings.

 

[Mike534x]

what "state" was the controller in? ie. was auto selected or otherwise or was it "officially" turned off with the OFF button.... or are you just hitting the "*" (AC function) to turn things "off". IF the thing wasn't turned OFF, then I do believe there are still "live functions" that will happen depending on sensor "levels" and settings.

I usually use "Auto" when turning it on, but each time it has come on I've hit the "off" circular button each and every time. It didn't come on today, and after holding "Auto" for a few seconds and then turning it off seemed to help. Going to be out driving around tomorrow, I'll be able to get a better idea if that solved it or not.

 

[TJBaker57]

FWIW, if anything.

Even when the OFF button is used, and the display reads "OFF" just above the external temperature on the HVAC module display, the module remains powered and active on the network, occasionally reporting this or that on the serial data bus.

 

[mrrsm]

...THAT...and the fact that on the Class 2 Network Bus... ANY other Modules that might be 'misbehaving' for other reasons can also affect OTHER Modules residing on the Net. Go Figure... Huh?

If you have a Tech 2... You might want to try using the *Ping All Modules* Feature and see what *Bounces* in return. Follow the Testing Features listed for Checking that HVAC Module "By The Book and The Bible" attached below:

 

[gmcman]

May not be related, but at least on mine, if you have the recirculate button pressed the A/C will turn on.

 

[Alfa-Norway]

Maybe you can try this. Disconnect the HVAC control module
Clear all DTCs.
Place the ignition switch to the OFF position.
Install the HVAC actuator.
Connect all previously disconnected components.
Remove the HVAC/ECAS fuse for a minimum of 10 seconds.
Install the HVAC/ECAS fuse.
Start the vehicle.
Wait 40 seconds for the HVAC control module to self-calibrate.
Verify that no DTCs have set as current DTCs.
Important: Do not adjust any controls on the HVAC control module while the HVAC control module is self-calibrating. If interrupted, improper HVAC performance will result

 

[mrrsm]

Some more Data on the HVAC Power Head NOT Turning OFF... Sometimes... A PCM Tech 2 Calibration Update can work wonders:

Bulletin No.: 02-01-39-007B
Date: November 05, 2007
INFORMATION
Subject:
Automatic Dual Zone HVAC Battery Draw
Models:
2004-2007 Buick Rainier
2003-2008 Cadillac Escalade Models
2002-2008 Chevrolet TrailBlazer
2003-2008 Chevrolet Avalanche, Silverado, Suburban, Tahoe
2002-2008 GMC Envoy Models
2003-2008 GMC Sierra, Yukon Models
2002-2004 Oldsmobile Bravada
2003-2008 HUMMER H2, H3
2005-2008 Saab 9-7X

Supercede:

This bulletin is being revised to add models and model years. Please discard Corporate Bulletin Number 02-01-39-007A (Section 01 - HVAC).
When diagnosing battery draws on trucks equipped with the automatic dual zone HVAC controls (RPO CJ2), technicians should keep in mind that the control head does not completely “go to sleep” until after 150-250 minutes, or up to 4-1/4 hours, from when the ignition key is turned OFF. This is a normal condition. In these cases, DO NOT replace the control head.