Byrant 90% Model 399A furnace. The Blower works fine and the filter is clean. Once the furnace starts there is no ignition. Where do I start with the ignitor or the spark generator.
Suggestions please.
Ron

What "starts"? The draft inducer? If so, the next device in the operating sequence to activate is the pressure switch. If the inducer runs, but no spark/pilot flame, check combustion vents/drain hoses for blockage.