No heat call. System is blowing cold air. Cycled the system on at the thermostat and diagnosed. Control board flashes an error code for pressure switch not reading correct pressure, or aux limit open, or gas valve coil open. Only the blower and inducer are running. After a few minutes, the error code stops flashing and the system runs heating. Let the system run and no other error codes showed up. Ran the heat cycle completely. Cycled the system on again and it repeats the same issue. System is a roof package unit. Unable to further diagnose due to rainy and windy weather. Will reschedule for anon rainy day to further diagnose.