A023_F: Auxiliary Limit Switch Open
Status
This is a critical fault. The furnace will not operate in gas heat modes but all other modes (e.g. cooling) should function .
Description
This fault is displayed when the IFC does not sense continuity through the Heat Assisted Limit Control (HALC).
Note: The fault code exists in the list of fault codes in the condensing gas furnaces, but the furnace as currently configured does not include an HALC control. There is a jumper wire in place of the control and, when the furnace control displays this fault, it generally means that the jumper wire is not making connection between the two pins on the control. The 802V furnaces do have a HALC
Expected Operation
When the circuit has been opened, the IBM (Indoor Blower Motor) is energized at maximum heating speed. The gas valve circuit is de-energized (if it was energized) and the IDM (Induced Draft Motor) is energized at high speed for 20 seconds after the fault is sensed. Response to thermostat cooling calls will take place as normal with IBM energizing at the higher of the two blower speeds (high heat or cool) when a call for cooling is also present. When the fault is cleared, the IBM will remain energized for the 90 second blower off-delay period.
Cause
No continuity between pins 3 and 5 of connector P1 on the furnace control. (96V)
Blower motor non operational or insufficient airflow.
Solution
Repair the jumper between pins 3 and 5 of connector P1 on the furnace control. (96V)
Determine the reason heat is accumulating in the blower compartment and resolve. May be defective blower or zone bypass damper is returning too much heat to the blower.
