'99 Grand Am heater fluctuation

My GA heater has begun intermittently blowing hot air, independent of the temperature control setting. It seems to happen most often after hitting large bumps and will correct itself if I turn the temperature dial.

I can come up with two possibilities. Failing Air Temperature Actuator or a dirty/bad Temperature Selector potentiometer.

Has anyone else seen this before?

With the key on, you should be able to hear the blend actuator move when you turn the temp settings dial.
It also could be air trapped in the heater core causing the fluctuations. Unualy caused from low coolant level or clogged core.

Sorry for the delayed reply!