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Replacement parts for WHIRLPOOL REX3519PQ0 29" ELECTRIC DRYER | AppliancePartsPros.com

See the attachment for the wiring diagram.

First recheck the vent by doing the following vent check.
You need both heat and air flow for proper dying.
Check that the temperature select actually changes the exhaust temperatures.
Check that the lint screen is clean. Sometimes they can get coated with fabric softener residue, greatly reducing air flow.
Check that the blower wheel is OK and clean.
Check the drum seals and all seals in the air flow path in the dryer.

Vent Check
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.