The timer advances when the heat shuts down on auto,if there is no heat the timer will not advance or if the heat doen't shut off the timer won't advance,is the dryer running hot or are the clothes really hot when the load is done on time dryed?could have a problem with the heating element,look at the element to see if it shuts off and comes back on as it cycles on auto?

Make sure the vent from the dryer to the outside is clean.
Reduced air flow can cause your symptom.

You can remove the vent hose from the dryer and operate the dryer in the automatic cycle.'
If the timer advances you know the vent needs cleaning.
Clean the lint filter housing also.
A flashlight helps to see all the way down the housing.