My heater/air conditioner stopped working all together. Loud noise from heater

I also noticed prior to this issue, the fan would blow high in the lo position. Can that be a problem in the switch as well? If so how would I go about fixing that problem?

If the fan motor was faulty the switch may be okay anyway. When they are going bad they will usually start surging causing this effect. Replace motor and if problem hi/lo persists change switch too.

check the blower resistor for corrosion