did what you asked reads 0 one thing dont understand can mess with it and will run fine for a couple hrs then flashes code switch is open and i jumped around it and worked fine just jumped it for a minute could it be in the board with a relay could one be getting hot after a time

need to add more to first post when i check voltage to pressure switch running reads 24 v on both sides when t stat temp is reached and every thing shuts down one side reads 4.2 should it read 4.2 then seams to me when shut down both sides should read 0 if so any thoughts thanks

dont know if this is the wright place but here goes got a nordyne m1mb 090 aaw light flashes that the pressure switch is open so have changed it new induser motor checked hoses draft is 1.5 checked exhaust as well as intake all clear any one got any thoughts thanks