Here is your parts breakdown
Model PAV3300AWW

Here is a service manual
http://www.servicematters.com/m...ibrary/docs/16023083.pdf

Sounds like a water level pressure switch problem
The switch is in the control console it has a tube which runs down to the bottom of the tub. As the water fills the unit, air is trapped in this tube when the air pressure in the tube rises to the set water level, the water level switch closes and the unit will then start agitation.

Often the problem is a hole or crack in the tubing or it leaks at the fitting or crud blocks the tubing at the bottom.
Remove the tubing from the switch and blow into it, that should clear a possible plug.
Check the tubing for holes etc.
Cut off about a half inch from the end and reconnect it to the pressure switch

Get a piece if tubing with same internal diameter attach this to the pressure switch. Let it start to fill, blow into the tube it should start to agitate. Should not have to blow too hard. If it will not stop filling the switch is probably shot.