AHX/MX Air Handler - Flashing Code 6

York Air Handler: AHX / MX

Re: Flashing Code 6

A Fault Code 6 results from the following sequence of conditions:

• If the limit switch opens for a long duration (Fault Code 4), the control will energize the blower until power is removed from the control (heat outputs will continue to cycle as the limit resets).
• If the limit switch opens for a second long duration period during a single call for heat (Fault Code 5), the control will enter a "soft lockout" which will keep the blower locked on and lockout the heat outputs for one hour.
• If the limit switch opens multiple times soon after the soft lockout reset (Fault Code 6), the control will enter a "hard lockout" condition.
  • During a "hard lockout", the control will keep all heat outputs de-energized until power is removed from the control.
  • The control will de-energize the blower five minutes after entering the hard lockout condition.

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

CHECKOUT:

1. Check for Water on Control Board

• Especially in counter-flow applications, the control board is extremely susceptible to water damage from condensate overflow.
  • If there is water in the base of the air handler, or if the control board has obvious signs of water damage ⇒ suspect a Bad Control Board

2. Check Limits & Board

• Turn off power to the air handler.
  • It is best to turn off power at the breaker box, as this test may bring you into contact with the inlet power wiring.
• Disconnect the white molex plug from the air handler control board.
• On the plug (not the board) check resistance between the Red and Brown wires.
  • No Resistance Red to Brown = Open Limit
  • Resistance Red to Brown = Limit Closed ⇒ Re-attach molex plug and re-power air handler.
    • Limit Closed + Code 3 or 4 = Bad Control Board

3. Check Blower Operation

• Activate a call for Fan by one of the following methods:
  • At the thermostat, turn the "Fan" switch to "On".
  • At the air handler control board, place a jumper wire between "R" and "G".
• X-13 Motor (AHX/MX)
  • Check high voltage plug for 230VAC
  • Check for 24VAC between "C" and "Red" at motor.
    • 230VAC + 24VAC on Red + No Blower = Bad Motor
    • 230VAC + No 24VAC = Bad Control Board

4. Check Heaters

• Ensure that there is no call for heat (disconnect W1 & W2).
• Check each heater amperage.
  • A heater drawing amps = Stuck Heater Relay or Bad Control Board ⇒ Confirm by checking DC voltage to the heat relays.
    • No Call for Heat + DC Voltage Present = Bad Control Board
    • No DC Voltage + Heater Energized = Stuck Heat Relay

5. Check Filter/Airflow

• Check air filter
• Check indoor coil
• Check duct static pressure