York Air Handler - Disable Limit Monitoring - Code 3

York Air Handler: MP, MX, MV, AHP, AHX, AVY

Re: Disable Code 3

The control board in the air handler monitors the limit switch in the aux heaters.

If the limit trips 3 times during a single heating cycle the board will go into a lockout and flash a code 3. This causes the fan to run continuous (even with thermostat off) and de-energizes the heating outputs.

• The diagnostic will NOT flash or provide any indication at the thermostat.

To reset: Line or Low Voltage Power to the air handler control board must be cycled.

AS A LAST RESORT it is possible to disable the board's limit monitoring without disrupting the limit shut-down of the heaters.

Be sure to check all other low airflow possibilities before performing this operation!

The BROWN wire on the 6-wire plug of the heater board provides limit monitoring.

Cutting and splicing the BROWN wire with the RED wire as shown below keeps all limits in series without allowing a Code 3 on the board.