My clare furnace will not come on. When I turn the furnace on noting happens. But if I turn the main fan switch on it comes on. But when I turn the thermostat up the small fan doesn't come on which in turn will not let the furnace work

You will need to use a meter to find out what is happening. There is no way to find out any other way. You go through a series of steps to find out what is wrong. Buy a meter and write back and I will tell you what to do or email me at [email protected].