how do i tell if ignitor is workin on ducane furnace
Well, observation is one way. Remove the front cover and watch it when there is a call for heat. Honestly, this is about all we can tell you untill you give us some more information like what sequence of events are happening when there is a call for heat. Draft inducer starting, etc.
Why do you suspect just the ignitor. There are a whole host of things that could be wrong. Is the power on to the unit?