I still think...
The fact that your I/M doesn't overfill shows that the I/M SIDE of the post filter valve works fine. Remember, the dispenser board does not have anything to do with I/M operation. You could rip the dispenser out of the machine and the I/M will still fill and harvest. Both pre and post valves work in tandem. When the Ice maker loads, both valves open to let the appropriate water flow to the I/M and since the diaphram that controls water to the dispenser on the POST filter valve may be stuck, water comes out the dispenser at the same time. When the dispenser is called upon to fill your glass with water, the valves open the other set of diaphrams and water flows. Again, if your post filter valve is bad, when you stop filling the glass, the pre filter valve turns off and the incoming water stops but with the post filter valve possibly stuck open on the dispenser side, water would still trickle out as the pressure built up in the filter releases and eventually stop flowing... A quick and dirty way of proving or disproving this is to remove the upper hinge cover on the freezer door and disconnect the wiring umbilical which effectively removes the dispenser from the equasion. When the I/M next loads with water and the water still comes out the dispenser, it's most likely the valve. If the I/M loads and there is no leakage from the dispenser then you may have an issue with the dispenser...
As a side note, to pull the dispenser housing, most units of that type have two 1/4" screws that can be seen after pulling the drip catcher tray from the dispenser. then, the whole face drops down slightly to disengage the hooks.
RCD
