Intermittent A/C & Heat will only come from defroster vent

[AZDENALI07]

I have a 2007 Denali and the A/C and heater will only come from the defroster vent even when cycling thru the settings every once in awhile but seems to be getting more frequent. The air is cold and hot when on A/C or heater. I have read on google posts of other cars of vacuum lines but wondering if anyone has any pics of the certain lines could be? Also wondering if anyone has any other thoughts on what it could be since it is intermittent. Not trying to get ripped off by dealership so so any help would be greatly appriciated. Thanks in advance.

 

[GM Customer Service]

AZDENALI07,

I’m sorry you’re experiencing this issue with your vehicle. This may be due to a vacuum line issue, however, I recommend having the vehicle inspected by a certified technician for an official diagnosis.

Please keep us posted.

Louis
GM Customer Service