I have a older 2-stage trane furnace 80%. First time checking the furnace the light on the board was flashing 3 times indicating pressure switch problem. I have no power going to inducer, diagnosis bad control board. after installing new board furnace fired correctly for 20-30 seconds and locked out again with pressure swicth problem. Both swicthes are open on iniatal call for heat. I never had this situation happen before just wondering if there is sommething i am missing. thanks alan.