davidlhausman

Odor coming from the AC vent when AC is on in my C5 Coupe according to my wife (passenger) any thoughts

3sACROWD

You don't describe the smell such as musty or moldy. Is the smell happening all the time or once-in-awhile?

The fresh air intake is in the cowl. You could try spraying with Lysol while you have the AC blower on high. I sometimes rinse that area with diluted Pine-sol while cleaning the engine bay.

jackthelad

There have been multiple posts on this over time; it's usually due to mold. There is even a GM procedure which involves drilling a hole into the HVAC plenum. I found that buying a spray can of stuff at the parts store that was labelled as HVAC de-odorizer or similar actually worked. As 3's said above, get the blower on high and generously spray the stuff in.

grantorino

Most odors are a result of constant operation of the recirculation mode. That mode disables fresh outside air from entering the interior. It's like taking a shower and not using the exhaust fan or opening a window. Mold and mildew form on inside surfaces.I rarely use recirc. unless it's extremely hot/ humid outside on any of my cars. And when I do use it, it's maybe ten minutes. For some odd reason people regulate the temperature with the fan speed rather than the blend door i.e. temperature ****? On a manually operated A/C regulate the temp. with the rotary temp. **** till comfortable On an Automatic climate controlled system set the temperature display to around 72 to 75 degrees and LEAVE IT ALONE all year. My C5 is an automatic dual zone unit. I rarely touch any button except for defrost in the Winter. I believe most functional problems come from changing the temperature drastically. 60 in the summer then 90 in the winter then turning the blower off then back on. A rare issue is the A/C condensation drain being plugged and allowing water to remain in the evaporator case causing an odor. I spray Fabreeze into the fresh air intake grille on the outside of the car where the wipers are parked. . Read the owners manual regarding use of the recirculation or MAX A/C button on any car. Sorry for the rant but this is a pet peeve of mine for many years.