Ez3720cee After completing the washing cycle the clothes are properly spun out. When the drying cycle kicks in, the unit fills with water... literally, a finger deep! The coin trap is empty. The drain is at the right height and appears empty (the washing cycle worked). Whats up?

Unplug the washer for 10 minutes and let the board reset. If it still is not filling correctly, then the pressure switch or load size switch is faulty. Appliance Parts Suppliers sells Samsung Parts in Bolingbrook, IL sells samsung parts.

I think you have to fill it with water first. My machine won't work unless the previous cycle has a chance to complete. i.e., it has to fill with water before the wash cycle starts, or it has to have water before it rinses/spins dry.

Could be the circuit board at fault

First, did you know that this machine steam dries clothes? The first thing it does on the dry cycle is to wet the clothes which it then heats to dry with condensation. There are better answers regarding this feature on fixya. But assuming that the dry cycle is working as well as it ever does, it appears that your wash cycle is not functioning properly. I would need more info to figure out why it is not filling with water / working at all.

I am having the same problem on a WD9900A. The wash cycle works great. Spins fast and clothes are completely rung out. Dryer cycle heats up well. Fluffs and heats cloths. At some point during dry cycle water is injected on clothes and they end up sopping wet; much wetter than after wash. Filter is clear. Outlet pipe clear and functions well. Possible problem with dryer timer? Or washer timing kicking back on?

You're a moron. This unit washes and dries. That's the whole point of it. Perhaps you should do some research before answering the question. the most likely cause is the water lever sensor.

Are you on well water? turn off the cold water to the washer and clean the screen filter out. do not leave filter out.
the machine probably has a cold only final rinse so it won't work properly.

Its likely the diaphragm on the water valve is clogged with hard water deposits and is leaking.
You can try to fix it by running some CLR cleaner through the water hose with it disconnected from the tap. or just replace the water valve.
a symptom of this issue is that water is always filling the machine. and you have hard water.
you can get to the water valves and take them out and replace/clean them by removing the top cover (3screws in top rear)
unplug the AC cord.
follow the water hose from the tap the first dual block you see has 4 wires and the hoses plastic connected to it. easy to remove.
But if the machine is not leaking all the time and the machine just wildly decides to activate the relays for water ( you will hear the solenoids click for more water flow then the issue could be the computer control unit.

Unplug the dryer and replug back up again.

Put on wash /let it go thru the cycles.

The problem lies with the water valve at the water entrance area; trace the pipe from where the water comes to dispenser. This should be done after opening up the top ( careful not to touch any part which could give you electric shock or anything) The pipe where the water gushes should be traced back to the inlet area, you will have to change this valve. To see the gush gently open the dispenser drawer.