Yep. Happened to my old TA-22 also... didn't have any tools on me at the time... don't you just love "roadside repairs"..it's amazing how inventive you can get to bypass the heater with just a car key as a screwdriver.
From memory it was leaking somewhere near the heater tap on the passenger side. It was only a small leak, but enough to be a problem... I would certainly recommend getting it fixed properly if you want to run a heater, if you don't want it anymore, then follow Major's instructions below.
The heater comes out pretty easily, just keep undoing bolts.. its bound to come out eventually..