Honda A/C acting funny

I've got a 91' honda accord with 271,xxx miles on it. Believe it or not, a/c still works. Still feel the compressor kicking in and it still puts out ice cold air. Only problem is, the ice cold air is coming out of only 1 vent, the vent thats on the far passenger side. All the other vents put out mildly warm air... but not hot air..any one have any idea of whats causing this?? Thanks for your help

Need to look under the dash and see if there is a duct partially disconnected that's contaminating the vent air with ambient air. The far vent might have it's own seperate duct, I'm not sure.

Does it blow evenly cold from other positions (floor, defrost, etc?)

Does it make any difference if it's on recycle or fresh? Sometimes they'll suck a plastic bag or something up under the dash on the passenger's side into the recirculate intake, and makes them do weird things in that position...

It should be that the freon is low. Recharge the system should solve the problem. If your AC is still using R-12, recharging will cost a lot. It's good time to convert to R-134a.