Whirlpool washer stops at rinse cycle?

I have a top loading Whirlpool washer that is 5 years old. It will complete the wash cycle and fill for the rinse cycle but won't start aggitation in the rinse cycle. It just stays there indefinately with a full tub of water. The timer also stops at the rinse mark. This happens in all modes (quick wash, permanent press, and heavy wash). If I play with the knob I can get it to spin, aggitate, fill, drain etc so I think that it may be the timer. Any other ideas or suggestions??