If I had tested the components I would have saved money. As it was I replaced both sensors on the blower housing and the heater coil housing. Then replaced the heater coil. Wala! Heat happened.
As a maintenance person I always recommend replacing all components related to a given problem at the same time. That way I do not have to worry about something else going bad the next week.
Kinda like replacing tires on your car. It is always good to get all 4 at the same time.