I have followed instructions from service which basically said that there is a small on - off switch in the bottom left for when I am hooked up to landline(120V) I believe this is also called "Connecting Electrical Supply" The switch is in the on position while hooked up to the landline. My question is ... does the furnace now heat using gas or is an electric heating unit engaged for heat. If the electric heating system is the method of heat source now instead of gas, then I must have a problem with that part because the gas heating system works just fine however the "electric" or other system does not work. The unit attempts to fire as I can hear what sounds like a spark but no heat. The blower fan turns on but no heat. The thermos stat calls on the heater but no heat. What am I not understanding about how this heater works?

Heating & Cooling - Thermos