[Shop-talk] Odd front loader washer overfill behavior

[Jim Franklin]

I have a whirlpool front loader model wfw9050xw00. It stops at some point in the wash cycle with an F8E1 error, which says low fill. In reality it has overfilled. If I drain it (power off button) and restart the load it's fine. 

I watched it fill yesterday and it shut off normally when there was enough water. Sometime later it overfilled. 

Internet says it's likely the pressure switch. A Toneluck B1 series:
http://thumbs.ebaystatic.com/images/g/YZgAAOSwB4NWyzAx/s-l225.jpg

I took the switch apart. It's a simple bellows, acted upon by air pressure in a sealed tube running from the bottom of the washer tub. As the water rises, the pressure in the tube increases, and at some point a curved strip of copper in the switch (like the clickers in dog training or Catholic church) gets bent and separates the contacts. I see no corrosion or other reason for the switch to be bad. Resistance when closed is .2 ohms and when open is infinite. 

Now I'm at a loss what else to try. The inconclusive nature of the failure has me stumped. I will look for debris in the pressure chamber in the tub, but the hose is clear if I blow through it. 

I'd appreciate any hints or experiences...

thanks,
jim