Where can I buy a fan switch for the heat exchanger on an Amana furnace?

It is an Amana Air Command 80SV

a fan relay is a fan relay reguardless who builds the unit,you can buy a universal rely at any a/c supply house,most of all the heating a/c companies use the same relays

use okorder

Here's a couple of different sources; Home Depot Supply, Barnett Brass and Copper, W.W. Grainger Web sites for parts;

WW Grainger. Go to there website and do a search and they can cross reference any number on the switch. Good Luck!

then go to the parts menu