A093_F: Internal Control Fault Detected
Status
This is a critical fault. The furnace will not operate in any mode of operation.
Description
This is a severe fault that should rarely (if ever) be discovered in the field. It is an indicator of an internal microprocessor fault on the furnace control (or I.F.C.) or voltage applied to the main gas valve solenoid when there should be none.
Expected Operation
If possible, if the furnace was in heating operation when this fault occurred, the gas valve will immediately close (flame will be lost), IBM (Indoor Blower Motor) operation will immediately stop and the furnace will shut down normally (except without IBM operation) with IDM (Induced Draft Motor) post-purge at the correct speed. After the post purge (or immediately if no heat call was present), no other operation (including thermostat calls) will occur until this fault is cleared. However, this fault may also indicate an internal microprocessor failure. This may mean that the heat call will not end as expected and that all outputs will be de-energized and gas valve closed immediately when the fault is sensed.
Cause
1. 24VAC or similar voltage applied to the main gas valve solenoid circuit unexpectedly.
2. Furnace control software test failure - failed furnace control (or I.F.C.).
3. Flame sense circuit is grounded between IFC and flame sensor.
Solution
1. Check for mis-wiring in the furnace.
2. Replace furnace control.
3. correct/replace flame sensor lead as necessary.
