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Parts for Whirlpool WED4900XW0 Dryer - AppliancePartsPros.com

See the attachment for your tech sheet.

FYI: All the dampness sensor does is advance the timer to off once the clothes are dry.

When you checked the heater element for continuity, did you also check to see if it is grounded?
If grounded it can cause the heater to run unregulated.
With the unit unplugged and both wires removed from the heater, both sides of the heater should measure infinite ohms to the case.

To eliminate the vent system as a possible cause try the following.
Unplug the unit and disconnect it from the vent system.
Now try a run.
If it now dries OK odds are the vent system needs checking/cleaning.
Be sure to check that the louvers on the outside of the house open correctly.

If you do not want any lint in the house.
Take a pair of pantyhose.
Put one leg into the other and then attach this to the dryer's vent.
Leave enough room so the pantyhose can balloon out like a windsock.

Both the above will let you check the temperature and the air flow.

Note: The above is not recommended for gas dryers due to carbon monoxide concerns.

Check that the vents at the back of the drum are clean.
Check that the lint filter/screen is clean.
Sometimes they can get coated with fabric softener residue and this reduces the air flow through the system.