HVAC acting weird!

[denalianyone]

I noticed more times than a few that my HVAC would reset upon turning the ignition off and on within a 5 min span. The display would act as if the battery died showing both the digital driver and passenger temp on.


Sent from my iPhone using Tapatalk

 

[swathdiver]

I'm not sure what you mean. While my display is different, it always shows the temperature setting for each side the way I have it configured.

 

[denalianyone]

It resets. Just say I have it set for 90 for just the driver side. I go to the store and come back the gauge resets to 74 for each side and the AC snowflake is engaged.


Sent from my iPhone using Tapatalk

 

[swathdiver]

All I can think of Ray is that the control head is bad but to know for sure would want to see the codes stored in the BCM or at least watch it operate with a bi-directional scan tool.

 

[denalianyone]

Ok thx, no codes as of yet


Sent from my iPhone using Tapatalk

 

[swathdiver]

Ok thx, no codes as of yet


Sent from my iPhone using Tapatalk

How do you know? These kinds of error codes do not set off the light on the dash.

 

[denalianyone]

How would I check for HVAC codes then?


Sent from my iPhone using Tapatalk

 

[R Fos]

Is your memory settings set to the temp it goes to under remote start and then starting. My older shortly Denali does that always has defaulted to memory setting when key in ignition.

 

[swathdiver]

Is your memory settings set to the temp it goes to under remote start and then starting. My older shortly Denali does that always has defaulted to memory setting when key in ignition.

I forgot about this, I never really move mine off 68 except in the summer when I drop it to 66.

You need a scan tool Ray that can check BCM (body) codes. Tech-2.

 

[Doubeleive]

my hvac has 3 settings
1. with the power off I can set the ambient temp for driver/passenger
2. press the auto button then set the temp I want driver/passenger/rear (a/c is auto on I believe as dehumidifier function regardless if you have it set to warm or cool)
3 press the power button and set the temp driver/passenger/rear/or defrost (with passenger disabled), a/c

when I cycle the key it remains wherever I left it last time I turned the key on, even hours or days later.

if yours does not stay where you left it last time you turned the key off then something isn't right, it doesn't change on it's own.

74deg is what it defaults to if you disconnect the battery for instance or unplug the control then plug it back in, so it sounds like yours is loosing the constant power connection when the key is turned off, I don't think a fuse would cause this but it couldn't hurt to check them and your grounds and maybe the plugs behind the control make sure they are all plugged in all the way
if you everything looks good you might have a bad control unit or it failed internally to keep power.