A056_F: Ignition Pressure Switch Open When Should Be Closed
Status
This is a critical fault. The furnace will not operate in gas heat modes but all other modes (e.g. cooling) should function if present simultaneously with a heating call (e.g. defrost call in dual-fuel mode).
Description
This fault indicates that the pressure switch is open when the inducer is energized. This fault can be displayed any time during the heat call and only after the pre-purge.
Expected Operation
(1) DISPLAYED BEFORE HEAT IS ESTABLISHED: The IBM (Indoor Blower Motor) will not be energized. The fault code will not be displayed until the IDM (Induced Draft Motor) has been energized for a minimum of ten seconds. The IDM will remain energized at the high speed (high speed is default pre-purge speed) for a period of five minutes after the beginning of the pre-purge attempt. After five minutes, the IDM is de-energized and second attempt at pre-purge is made (as long as the heat call is still present). This cycle is repeated indefinitely until either the pressure switch closes or the heat call is lost.
(2) DISPLAYED AFTER HEAT IS ESTABLISHED: in steady-state heating mode, it will wait a minimum of 2 seconds before de-energizing the gas valve relay and shutting down the unit. It will perform a 2 minute cool down period before proceeding with pressure switch proving if the heat call is not satisfied.
Cause
1. Blockage in the exhaust vent.
2. Faulty or disconnected inducer.
3. Faulty control board (inducer drive circuitry).
4. Loose or faulty wiring.
5. Disconnected, blocked, split or cut pressure switch hoses.
6. Faulty Pressure switch.
Solution
1. Check the vent system for blockage and proper termination and repair as necessary.
2. Repair or replace inducer and/or inducer wiring and/or electrical connections.
3. Replace control board.
4. Check wiring and connections. Replace and/or repair as necessary.
5. Replace hoses as necessary.
6. Replace the pressure switch.
