I set my dryer at 40 minutes. after 1 hr the dryer is still on and the timer still says 40 mins . clothes are dry

Dryers can base their drying time two different ways. If you are using the "dryness" settings, when you first start the cycle, the timer will show a specific time. If the contents dry fairly fast, the moisture sensors in the dryer will reduce the remaining drying time. This may be what is causing your changes. If you want a specific time on the dryer, or the dryness settings aren't getting the clothes as dry as you'd like, opt for a "timed" dryer setting, where you choose the drying time. This bypasses the sensors.

Type Maytag dryer timer problem into YouTube and see if the video comes up, thanks!

Dryer has a moisture sensor that detects the clothes are dry so it shuts off earlier. If the clothes are still damp then the dryer vent may be plugged and causing the unit to run hot or not able to fully evacuate the air from the machine. Clean the vent and make sure it's completely free and try again. If it short cycles again and clothes still damp you may have a sensor controller issue.

Does it shut down completely? If it does, and the timer ceases turning, your problem may be a blocked vent pipe or Lint buildup.Your high limit switch is designed to kill power to your heater coils and sometimes the motor in case of overheat.

For a gas dryer:
Assuming the dryer is working properly and the control cycles are ok, look for things like a restricted venting system which inclides the exhaust, lint screen, etc. This would be the large pipe connected to the dryer exhaust that vents outside.

If it's an electric dryer, there could be issues with heating elements, thermostats, a control board, the timer, etc. Also check for any excessive lint build-up.

Maytag Bravos 400 Series Dryer purchased August 2009 - November 2009 required repair as I also experience the timer readjusting itself to excessive extended drying time when clothing was bone dry and hot. Sometimes extended to 1 hour 40 minutes! Serviceman stated problem was the Sensors in the dryer. Part number 8577274 Thermister and "Old Ohmed out open" whatever that means as listed on my repair ticket. Have not had that particular problem since. Make sure your dryer vents from dryer to outside are clean and clear of lint. Will help immensely. I have many other issues with this dryer it has been down FOUR times in 9 months. Fighting with Maytag to replace this lemon!

My twin stacking whirlpool washer/dry. The timer switch kicks on but does not dry clothes kicks off after 5 mins but, clothes still wet.

hi thanks for the question in the ge dryer theres 2 elements so if one is not working you only get half heat i would check the heater thanks the appliance doc

you have to change out the timer motor...
http://www.partselect.com/repair.aspx?appliance=dryer&part=dryer-wont-heat

Generally, timers and sensors are separate but work together. When the sensor is on, it 'knows' how damp the clothes are. You decide how dry you want as an end point. At a certain point, the sensor runs the timer for a certain additional length of time to finish the job to the point you select. Otherwise, the timer is just that. It sounds like either the sensor or the timer board is bad.