thanks for taking the time to read the post.
this is a trane xr90 gas furnace. the inducer fan runs constantly. the unit will run and meet the set point on the thermostat and then shut down except for the inducer fan running. the unit will not start again unless i manually reset the pressure switch - gently move air in the tube to the pressure switch.
i called for service and at that time it was an intermittent thing and the tech could not pinpoint the problem. since the service call i have identified the above sequence to get the equipment to start.
in addition to the service call i had the pressure switch changed and checked to make sure all condensation lines are clear.
any ideas as to what is causing this unit not to operate correctly?