If you are sure the vent is clean to the outside, I would replace the thermister, that sits on the vent tube. The part # is 3976615. I would take the bottom front panel off, and of course the dryer is unplugged, and then I would pull the lint filter out, and take nthe filter assembly off, and also be sure that it is not full of lint. Plus, it will give you easy access to thermister. Tom Appliance Educator, Appliance Parts, Washer and Dryer Parts, Refridgerator and Freezer Parts, Stove and Oven Parts