What is the best way to tell if the Fan is working. Most models you can see the fan spinning.This type you cant. Some times I see condensation around the vent and this may indicate an inpoperable fan.
This unit also didnt have a cabinet safety switch. Is this required?
I would assume that there must be some moving parts which would indicate that the fan is running. You couldn’t see the fan shaft/axle?
The “cabinet switch” has been required for the last twenty+ years, but it’s located in the return air compartment, not the upper cabinet. It’s purpose is to keep byproducts of combustion (from the burners) from entering into the return air compartment and being distributed into the home.