[johncatania]

I have a Heil gas furnace Model N9MP1/MP2 that is igniting fine, and I do see a flame so yes it begins to heat the air. The fan comes on and heat begins to flow through the vents then a minute or so later, the flame cuts out and then immediately the flashing green light starts blinking three times. The furnace has some type on it that says three blinks means fauty pressure switch. I blew and sucked air into the rubber hose that comes from the pressure switch. I did hear a clicking noise. Do I need to replace my pressure switch??

[Grady White]

Probably not. It sounds like the switch is working properly. Something is causing the switch to open. One of the most common problems is a blocked condensate drain line.