When t-stat calls for heat the combustion blower starts, the glow plug glows but gas valve doesn't open and burn doesn't ignite. The combustion blower continues to run. Is this a problem with the pressure switch? Does it need to be replaced? :confused:

If the ignitor is glowing then there is no probem with the pressure switch

Do you hear gas blowing in? Sounds like no gas, bad gas valve or bad control board

Also, make sure you have gas present, make sure the burners are not rusted closed, if the burner in front of the ignitor is plugged the burners won't light.