Hi,

Kenmore Series 90 dryer

Kenmore is made by several different companies....model#?

http://www.applianceaid.com/model.html
http://www.applianceaid.com/searscodes.html

In either the auto dry mode or the timed dry, the
timer doesn't advance, at all

Check for power to the timer motor with a volt meter, power there but
no timer movement/advancing = timer problem.

jeff.
Appliance Repair Aid
http://www.applianceaid.com/