I have a bryant model#395baw036080

Are you experiencing a problem, or just curious? There is a draft safeguard switch situated near the flue outlet. It requires manual resetting if tripped, and generally indicates a problem with the flue draft (i.e. blockage, high wind, collapsed chimney liner).

What does it look like

I can't get my air or funace to come on. I changed the door switch and motherboard. My breakers got power and door switch.

It would resemble one of these.

3 methods of checking a cap tube system for correct charge

There is 1 method: superheat. Check this out. http://www.hvacsalesandsupply.com/Linked%20Documents/Tech%20Tips/Proper%20System%20Charging.pdf