If it's the older 24junior and the pump then fan runs and then it seems like it's going to ignite but then the red light starts flashing it probably will be the low water pressure switch on the top right hand side of the heat exchanger that's blocked if the fan runs for about a second it will probably be the pcb....
Gary, November 2010
If it's the condensing model (Greenstar Junior 24) check the 3/4" dia white condensate pipe isn't blocked. The condensate that runs through this pipe is prone to freezing in very cold weather.
