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Just to be sure that it is not a venting problem 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 the air flow and that when you choose different temperatures it actually does change the exhaust air temperature.