My Kenmore 110.86870100 electric dryer is having some problems...

1. Timer won't advance when in 'auto' mode, timed dry advances okay, but still takes too long to dry.

2. Drying time is taking at least double what it used to. Seems it doesn't get as hot - towels take forever...

I checked the timer resistor at around 5K ohms.
Checked the thermal fuses and are not 'open'.
Checked the temp knob and resistance changes for each setting.
Vents are clear, inside and to the outside.

Do you think I have a defective timer, or can one of the thermostats be causing this? (not sure how to check out the thermostat.. ).

Edit: Heating element is not shorted... exhaust temp doesn't seem anywhere near where they should be...

Help!

Sounds like your vent system is plugged up does it come out the side of your house or up through the roof if it is plugged up it will cause both of the problems you stated