In 'auto dry' mode, dryer will not automatically shut-off - continues to run long after clothes are dry

Lastly check your moister sensor. ( located inside the dryer door usually) Especially if machine seems to shut down early and clothes are still wet.
Test with a meter at room temperature and it should show continuity.
A failed moisture sensor will affect the dryer run time in the automatic moisture sensing cycle but it will not affect the heating of the dryer or the timed cycle. Which are reflected by the thermostats.

Read more :http://www.ehow.com/info_12203962_check-dryer-thermistor.htmlGOD IS So GOOD !!!! AND THAT'S WHY MY ADVICE IS FREE
How to Check Dryer Thermistor eHow

There is a sensor that the clothes have to touch when the drum spins. This sensor measures how wet the clothes are. If you don't have enough of a load in the dryer then the sensor wont detect the dryness. Or it could be a bad sensor or connection or main board.

FIRST OFF IN THE AUTO DRY MODE THE DRYER USES THE MOISTER SENSOR AND AS LONG AS THE MOISTER SENSOR DOES NOT DETECT HEAT OR DRIED CLOTHES IT WILL CONTINUE TO RUN FOREVER.

NEXT AS FOR UR NO HEAT:

ELECTRIC Dryer no heat or little heat, or shuts down to fast:

Check your venting and lint basket. Check blower for lint build up and blower wheel obstruction., test by trying to turn the wheel manually by hand (should be easy) May have to remove cabinet or front/back plate to get to it)

Next check the heating element itself with a meter for continuity OHMS CLOSED CIRCUIT. If not its defective or has a short if its grounding out? Which in turns causes blown fuses or thermostats or overheating.

Check dryer Terminal block prongs both outside prongs should give combined 220, and 110 each if u check 1 outside & 1 center (ground) prong. Also check house electrical outlet for full voltage. 220 because if u only get half or 110 volts you will be able to run the machine which uses only 110 to run motor but not the heater which uses a full 220,

Check the thermal cut off, the cycling and the hi limit thermostats.
For continuity or OHMS. If no ohms or resistance they need replacement.

In some dryer's the control panel relies on a thermistor rather than a CYCLING thermostat to regulate the drum's air temperature by monitoring the component's resistance changes; resistance goes down as temperature increases and up when temperature decreases. Once the drum's air temperature reaches a certain level required to dry clothes, the control panel shuts off the heater. The panel will turn the heater on again and begin another heating cycle when the thermistor indicates that more heat is needed to keep the air temperature constant inside the drum

Lastly check your moister sensor. ( located inside the dryer door usually) Especially if machine seems to shut down early and clothes are still wet.
Test with a meter at room temperature and it should show continuity.
A failed moisture sensor will affect the dryer run time in the automatic moisture sensing cycle but it will not affect the heating of the dryer or the timed cycle. Which are reflected by the thermostats.

Read more :http://www.ehow.com/info_12203962_check-dryer-thermistor.html

-Sounds like the timer motor is not working .
-Check and replace it.

Good Luck

Mai

If your dryer seems to run forever, it could be because of a clogged vent or internal ductwork. Your dryer may have an automatic cycle that turns off the dryer when the clothes are dry. It does this with a special thermostat or moisture-sensing system.Normally, this is what happens during an automatic cycle: The thermostat tells the dryer to heat until the interior of the dryer reaches a pre-set temperature--say 135 degrees. When the dryer reaches the pre-set temperature, the thermostat tells the timer to begin advancing. (If there's a moisture sensor, the timer advances only if the moisture content of the clothing is low enough.) The timer advances until the interior cools, then the thermostat tells the timer to stop advancing, and tells the dryer to start heating again. This cycle continues until the clothes are dry. But...if the vent is clogged, the dryer may never reach the proper operating temperature, so it doesn't send the signal to the timer and the dryer continues to run indefinitely, even if the clothes are completely dry. To fix the problem, clean the vent and/or internal ductwork.

Hi, If your dryer seems to run forever, it could be because of a clogged vent or internal ductwork. Your dryer may have an automatic cycle that turns off the dryer when the clothes are dry. It does this with a special thermostat or moisture-sensing system.
Normally, this is what happens during an automatic cycle: The thermostat tells the dryer to heat until the interior of the dryer reaches a pre-set temperature--say 135 degrees. When the dryer reaches the pre-set temperature, the thermostat tells the timer to begin advancing. (If there's a moisture sensor, the timer advances only if the moisture content of the clothing is low enough.) The timer advances until the interior cools, then the thermostat tells the timer to stop advancing, and tells the dryer to start heating again. This cycle continues until the clothes are dry. But if the vent is clogged, the dryer may never reach the proper operating temperature, so it doesn't send the signal to the timer and the dryer continues to run indefinitely, even if the clothes are completely dry. To fix the problem, clean the vent and/or internal ductwork.

If your dryer seems to run forever, it could be because of a clogged vent or internal ductwork. Your dryer may have an automatic cycle that turns off the dryer when the clothes are dry. It does this with a special thermostat or moisture-sensing system.

Normally, this is what happens during an automatic cycle:

• The thermostat tells the dryer to heat until the interior of the dryer reaches a pre-set temperature--say 135 degrees.
  
  
• When the dryer reaches the pre-set temperature, the thermostat tells the timer to begin advancing. (If there's a moisture sensor, the timer advances only if the moisture content of the clothing is low enough.)
  
  
• The timer advances until the interior cools, then the thermostat tells the timer to stop advancing, and tells the dryer to start heating again.
  
  

This cycle continues until the clothes are dry. But…if the vent is clogged, the dryer may never reach the proper operating temperature, so it doesn't send the signal to the timer and the dryer continues to run indefinitely, even if the clothes are completely dry. To fix the problem, clean the vent and/or internal ductwork.

try to get the manual for the dryer you got and locate the moisture sensor if this sensor is bad what happen is that the automatic timer thinks that the clothes still wet and continues to dry once the sensor detects no moisture then it shut off the dryer normally is located behind the dryer on the exit line of the air duct and tested for conductivity and see if is good or not

On auto dry cycles, the cycle is controlled by moisture sensing bars located on either the rear or front bulkhead, ( visible inside dryer ) if the moisture sensor bars are shorted together (normally by wet clothing) the dryer will continue to run. If the dryer continues to run when the clothes are plenty dry, check and see if there is anything stuck between the sensor bars, (sometimes a metal sequin will cause this) or see if they are damaged. If not, you may have a problem with a timer contact, if the timer advances and stops moving at the same spot each time, I would suspect the timer. If this is an EvenHeat dryer, examine the control board located to the right of the timer in the control panel, for any burned components. Hope this helps.

Faulty selector switch or control card. There is the possibility of a faulty moisture sensor. Can you operate the machine in manual mode ?