My Maytag Atlantis Gas Dryer (MDG8400AWW) never shuts off until the front door is opened. It runs and heats once started but the timer does not advance regardless of setting and the blue moisture sensor light never changes color to yellow then red indicating cloths are dry even though everything is bone dry. The lint basket is cleaned after every use and I have checked the vent for possible blockage - even ran the dryer with hose detached from vent to make sure there is no obstruction. It continues to run and put out hot air without timer advancing regardless of setting until I open the door to stop the cycle. What parts are needed to fix the problem - timer, moisture sensor? I think the dryer is about 4 to 6 years old (came with the house so I am not positive).

Yes, I have fixed the problem by replacing the Dryness Display Assembly (PCBA Board) that is found under the control panel cover (close to the timer). As moisture is pulled out of clothes (as cloths dry) it sends signal to timer that allows it to advance. Make sure your vent and vent hose is totally clear of any potential lint blockage, sever kinks etc. I also used rubbing alcohol to clean the surface of the black/silver SENSOR BAR ASSEMBLY that is located inside the tumbler on the front panel that the door is mounted on close to the lint basket (to clean any potential residue from fabric softener sheets on the moisture sensor feeding info to the Dryness display assembly board) but later changed it as it was a very cheap part. I have been told that the majority of the time it is the Dryness Display Assembly board or the sensor bar assembly that are the problem and not the timer itself. My Maytag dryer is the MDG8400AWW and here is the link for the Dryness Display Assembly part and where I ordered the part Whirlpool 33002734 Dryness Display Asse - AppliancePartsPros.com They currently do not have the Sensor bar assembly but I bet just wiping it clean with rubbing alcohol is all you need to do to it - if anything at all. Easy company to work with, great return policy, and will replace defective parts or parts that fail under warranty with just a phone call. Good luck.