I have a 80 uhg. The thermostat calls for heat, the fan turns on and the igniter heats up, flames come out for about 2 seconds, then turns off. This repeats 4-6 times.
The Diagnostic lights flash "Alternating slow flash"
The Lennox book says Watchguard- burners failed to ignite

Is there an easy way to fix this or do I have to call for service.
If I have to call for service, what price range am I looking at?
Thank you,