2006 WRX A/C loosing refrigerant

Hey guys, I have a 2006 WRX wagon with around 240k miles on her. For the last several years I have been adding R134 to the system to get me through the summers. Now it doesn’t last 2 weeks. I used a sniffer to check all the orings under the hood and all checked good. I put the sniffer in the vents and it gives a slight signal of leakage. So… I replaced the condenser and it still does the same thing. After playing with the controls I found that the leak is worse when the A/C is selected off (fan still blowing full). With the A/C switched back on, it barely detects.
Any ideas out there that might help me figure this one out?? It’s getting pretty damn hot here in the Midwest and really don’t want to drive my pickup.

Sniffer going off in vents is a leaky evaporator, not a condenser--it goes off more with a/c off because low side pressure at the evaporator is more when the a/c is off. Try the sniffer at the evaporator condensate drain on or below firewall and see what it does. Be careful not to suck water in your sniffer.

Thanks for replying. I meant that I replaced the evaporator. The part in the dash, not the part up with the radiator. I was looking for the reason for it to leak with the system off and you answered that. I still have the old one so I’m going to pressure test it and see what happens. I’ll also check the drain like you said. Quite possible that I got a bad part.

Okay, so I pressurized the old evaporator up 90 psi before it blew on my hoses of. The old evaporator doesn’t leak. I checked with the sniffer at the evaporator drain and don’t get a leak signal. After checking in the cabin again, the sniffer still goes off briefly from the vents after I select the AC off. It doesn’t go off at all when the AC is on. With the old evaporator pressure testing good, I really don’t think the new one is bad. Is there anything else it could be. Everything I read says it’s always the orings at the pump. The sniffer gets nothing from there.
Aside from a shop that does AC repair for a living, what else can I look at?