Arrived on site to perform diagnostic on 2 13 year old Goodman furnaces. Homeowner states that neither of his 2 systems are not heating, Have not worked for about a month. Did mention that he did have a power outage before they stopped working. Cycled upstairs unit for heat. Heating sequence engaged, but cut off after the ignitor turned on. Circuit board flashing code for open pressure switch. Tested switch and switch is opening and closing as it should. Bypassed pressure switch and tried cycling unit, circuit board is still stuck on open pressure switch code. Continued resetting board until code finally cleared and unit kicked on. Circuit board is failing intermittently, would recommend replacing circuit board on this unit, but system is operational upon departure. Cycled downstairs unit for heat. System automatically goes into pressure lockout. Tested all pressure switches and they all open and close normally. Tried resetting circuit board numerous times and it still goes straight