My a/c system has a small leak. I can charge it up with a refrigerant that has a stop leak in it, and it will cool for about a month. The only problem is that after I charge it, using stop leak or not, after it leaks back down, I get this god-awful smell out of the vents when i want to run fresh air, or even the heater, cuz the nites are getting cooler now. Does this mean, my leak would be in the evap core? or something else. thanks

 

Probably a leaky evap core. It's a common problem on 2nd gen rams, and it's not fun to fix.

BTW, you're not recharging the system with one of those do-it-yourself kits are you? I hope not. Those kits ususally contain flammable gasses that can cause engine bay fires if a leak develops. Not good! You're safer taking it to a REPUTABLE shop to have it recharged. It may cost more, but it's safer. And I say "reputable", because some shops also use the same flammable gasses to recharge AC systems. [:'(]

 

Try shutting air off about a 1/3 mile before your destination. Keep the blower on though. Mine had a musty smell just like you're talking about. If you leave air on when you shut off engine the plastic air box stays cold, and with no air flow, moisture collects in there and gets moldy. Seems to work for me.