Help!

The furnace is clicking like it wants to come on. If we take the furnace door off we can set to manual and it will come on and keep giving us heat. But when set to automatic it will not come on at all. I cannot find a manual anwywhere for this furnace. Hoping to figure this out without calling a furance company.

Does anyone know what part I might need?

Thank you for any help we get.
Cheryl