How does a Whirlpool front load washer detect load balance prior to spinning?

[wildimaginations]

I have a Whirlpool front load washer WFW9470WW. Customer is complaining that once in a GREAT while, it will not spin. Water does drain out but the clothes are still dripping wet.  I already checked the drains and it's clear.  The customer claims that she does fill the unit between halfway to 3/4 full of laundry. I tried to explain to her that the load is unbalanced and the machine cannot spin the clothes. The customer feels that there is something wrong with the unit but it doesn't break down all the time so she's asking me to research into this. How does the unit detect spin balance? Is it by the motor control? Are there any service updates on this unit? Any help or suggestions is appreciated.

[Joebeef]

If I remember correctly the CCU senses it's taking too long for the motor to get to full rpm then stops the spin, agitates then tries spin again...the same as if you have a long drain.

[LowSL2]

I've seen a lot of this issue. I think the control will try to balance the load for 7 or 11 minutes. If it can't balance it, it will just complete and unlock the door with no error codes. I think you get an unbalanced error in agitate or the first spin cycle.  I would check to make sure its solid against the floor and the suspension is in good shape.

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[Wedgeman55]

The unit detects the spin balance through the MCU>  If load is not balanced,  the amperage vs the speed of the drum is out of wack.   Don't forget motors on these have a tachometer that tells controller what the speed is,   and also report amperage.   The controller can detect motor amperage and as it attempts to go clockwise,  then counter clockwise, then distribution mode then spin,   it will read these values.   If it is not what it should be,  it will attempt to start again.   I have found,  once in a while,   certain loads cannot be balanced.     Best advice to customer is to make sure you run full loads,  not small loads.    The loads should also be of similar weight clothes.    If you run a big bath towell and a few pillowcases,   this may not be able to be properly balanced.