Auto Air Conditioning & Heater Repair: Air Conditioning Question, rear vent, ac evaporator core

Question
Re: 2003 E 350 Ford Van w/front & rear air.  AC quit working.  Thought it need re-charged and added freon.  The freon blew out the vents inside the vehicle.  Someone told me this is the AC evaporator core.  This vehicle has two evaporator cores (both in black plastic boxes).  How can I identify which one is leaking? Can I tell by opening the black box and finding oil? Will it be wet in the box? Or do I have to invest in the UV kit to find the leak? Any help you could offer me would be greatly appreciated.

Thank you.

Answer
Richard,
As you know, all vehicles with front and rear A/C have two separate evaporators, but they are not in the same location. Your front evaporator is what cools the front of the cab, and your rear evaporator... the passenger/cargo compartment. Likewise, both the front and the rear have their own separate duct-working. If the refrigerant blew out your vents in the dash, it is your front evaporator core that is leaking. If it was the vents that are either in your headliner or floor panels in the rear (any vent behind front seats) then it is your rear evaporator that is leaking. These ducting sstems are as I said... completely separate from each other and it would be impossible for the front evap to be leaking and blowing out the rear vent or vise-versa.
If you are looking at two plastic housings under the passenger side dash board, and that is what you are refering to... one is your front evap, the other is your heater core. Your rear evap and heater core is located in the rear driver's side panels right behind your rear tire.
I hope that I was of a little help. If so, please don't forget to rate this answer. And if I can do anything furher to help, please do not hesitate to ask. Thanks for the question and good luck in everything.