Auto sense dryer dryes sometimes and won't dry on time cycle

try cleaning the 2 silver senser bars located inside the dryer drum on the door side with isopropyl alcohol and lint free wipes,these bars sense moisture and control timer speed,and when they get coated with the chemicals in dryer sheets they become coated and can no longer sense the damp clothes (these sensers use capacitance to sense moisture)

Verify that the wrinkle prevent switch is good. If so, the timer is likely the problem. Sometimes the switch contacts inside the timer can be cleaned to restore operation, bit it is a tricky item to disassemble and reassemble.

AD is auto dry you may need to clean the sensor or you may have a fauilty one ...Auto Dry Loads dried using the Towels, Heavy Duty, Normal, Perm Press, and Delicates cycles will dry automatically at the selected temperature to the desired dryness level. The dryer uses sensing bars to sense the moisture level of the load as it tumbles through heated air. Auto Dry cycles save time and energy and protect fabrics. The estimated drying time will be displayed for about 5 minutes, then the outside of the display will light up in a circular track to indicate the drying time is automatically being determined by the sensors. When the load has reached the selected dryness level, it will continue to tumble, unheated, during a Cool Down period. This helps reduce wrinkling and makes items easier to handle during unloading. The estimated Cool Down time will be displayed. Drying time varies depending on size and dampness of load and fabric type. If the load is too small or almost dry, the sensing bars may not detect enough moisture to continue the cycle and the cycle may end after a few minutes. Select a Timed Dry setting to dry such loads. Room temperature and humidity, type of installation and electrical voltage or gas pressure can also affect drying time. For cycle selection turn the knob on the front of the dryer control panel. The light will illuminate next to the cycle selected. The following is a brief description for what cycles should be chosen for certain items and materials to be dried.

Clean the lint filter(s) and verify unobstructed dryer exhaust. 99% of the time the dryer exhaust is clogged.

If you use a lot of dryer sheets, it will build up an oily residue on the sensor strips causing a "false" reading. Light sandpaper and alchohol over the strips should clean them well. Another possibility, is if you have a mixed load, ie..towels, socks, jeans , if a sock or something light keeps hitting the strips, the dryer thinks the whole load is dry (it doesn't know there are different thing in there) Try keeping loads similar when using auto dry.

try timed dry cycle instead of the auto-sensing setting. In your drum if you have auto dry such as less dry normal dry and more dry, There is a sensor sometimes in the drum and sometimes in the exhaust right after the blower. If in the drum then your clothes brush by this and if moisture is sensed then it keeps on drying. With your rack the clothes can't touch the sensor so it tells your dial to turn and that items are dry which in fact are not. Try this and see how it does.

Have you checked the entire duct run. When dryer vents should feel like a hair dryer on high blowing outside

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.

first take the venting off the back of the dryer and dry a load if dryes normal replace venting if takes a long time to dry have a repair man clean the dryer

it can work on timed dry with out the strips. they are only in use during auto dry cycle