Smell from A/C

A/C funtional diagram

So everyone reading this thread understands how AC works, here's a flow diagram. NOTE the blue coils are the evaporator coils inside the car that can get mold on them.

 

If you look behind your lower glove box (that is, if you are familiar with removing the lower glove box) and just above the cabin filter there is a servo-door that is usually "open". This allows air from the cabin to be recirculated thru the system and closes off most of the air from the outside.

When you press the outside air button, that door closes like a clam-shell and draws in air from the vent just under the the passenger wiper blade.

 

It sucks

Here is a old vs. new evap off a Volvo 850




You don't want to see the strip down pics of taking the dash down to the firewall...

 

@pakitt: The easiest way to remove the lower glove box is to first gently pry off the plastic damper piston (black and to the right) from the box. I say leave it connected on the backside so there's less confusion on how to reconnect it later. The ring part just slips off the round snap on the box. Now very carefully use a flat screwdriver and pry gently against the plastic lip on same side of the "frame" for the lower box using the glovebox as the brace for the screwdriver. It will move just enough to allow the tab on the back of the glovebox to come forward past the lip. Now carefully repeat this process for the left side. Both tabs are now free of the frame. Rotate the box on its hing toward you and then gently lift up on the box and it will "unclip" from the hinge on the bottom. Store your lower box in a clean area so as not to scratch or guff the front.

You now have access to the filter and main blower section. Yes, that "squirrel cage" blower is the only fan for the AC system. You might want to remove the cabin filter (the right side of the access just has a simple pry snap) and check it for debris. Also, smell it to be sure it is not culprit for the odor you smell. As per the diagram I included here, the evaporator coil is to the left and below this filter area. I have not discovered a way to get to it for a coil cleaning as yet. But if it has mold on it, that could be the source of odor too. Maybe if you spray some Lysol Fresh Linen scent in there while while the blower is running, it might cure the smell. Yes, it will come thru all the vents and be strong for awhile. I've done this on mine with some success but it's not the same as a coil cleaning.

Here's another trick I use: There's a product called "Little Trees" which is a hanging air freshener. I get the "New Car Scent" ones and put one BELOW the cabin filter carefully resting on the plastic ribs so it can't get sucked into the blower. I also cut off the string so it can't get in the blower either. This provides an ongoing nice scent which lasts about a month or so. For some, it might be a real pain to take out the glovebox to replace the Little Tree when it wears out.

You asked about the recirculating mode and as I see it, that "clam-shell" door when open is the intake source for the recirculated air. When closed, most of the air is drawn from the grille intake below the passenger wiper.