without looking at it it's hard to say however,if the pan was full of water then it must be holding holding water so the pan doesn't have any holes in it.i would try removing the drain pipe or tube whatever it has and see if it is clogged with rust.if after you remove the tube and the pan is still holding water then poke a wire or something into the outlet hole and see if you can unclog it.if it has a limit check the float and limit switch.or get a second opinion before you spend 1500 dollars.