jrockgts197

It's pretty normal. Every single car I've ever owned had this happen in one way or another. I had a friend with a 96 Z71 truck that blew hot air through the floor vents horribly, which he called his "free heat" lol. I honestly think it comes from aging seals or mechanisms on the blend doors, which would explain why max A/C would temporarily alleviate the problem (recirculation mode, blend door shut). You're doing better than my co-worker, his windshield freezes from the inside in the winter, and no combination of climate settings on the dash can fix it as long as the truck is moving - and it's a 2011 model lol.

pascal

It was sarcasm, lol.
Nuke is known to indulge in it since this past winter at least.

To stay on topic, check and see if your cabin air filter is OK or hasn't shifted.
That could be an issue, if not, the members already answered your question pretty much.

onederful100

I am super **** about everything in my Mustang.
when the AC isn't on, i close the vents.
when the vents are closed they all must be perfectly horizontal.
in my honda civic, warm air comes in too. unless i switch the vents to circulate instead of outside air.
that is just like what another post said about switching to max AC for a second, then turn it off.
Max AC is recirculating the cabin air and closes the outside air vent.

Goldenpony

My '06 has always done this too.