York Air Handler: AHX/MX
Re: Fan Running Continuous - No Fault Codes
The customer reports that the indoor blower runs continuous.
► This is normally associated with a Code 3 on the air handler board, but in this case there is no fault indication on the board.
Qty |
Possible Causes: |
|
Bad Control Board |
2 |
Bad X-13 Blower Motor |
|
Thermostat set to fan "On" |
|
Shorted Low Voltage Wiring |
|
Bad Thermostat/Subbase |
Checkout:
1. Check the Thermostat
- At the thermostat, make sure the System is turned "Off" and the Fan is set to "Auto".
- Check to see if the indoor blower shuts off within 60 seconds.
2. Check Low Voltage
- At the air handler, remove the blower cabinet door.
- ► If the blower is running, be careful with the blower door insulation (it will try to pull off).
- Check for 24VAC between "C" and "G", "Y", & "W".
- No Power → Step 3. Check Control Board
- Power Present ⇒ Continue
- Remove the powered low voltage wire from the air handler board.
- Blower Continues to Run → Step 3. Check Control Board
- Blower Shuts Off ⇒ Continue
- Check for 24VAC between "C" and the removed wire.
- Power Present ⇒ Pull the thermostat off of the subbase and check (at the subbase) for power between "C" and the powered wire.
- No Power = Bad Thermostat
- Power Present ⇒ Remove the powered wire from the subbase and check for power between "C" and the wire.
- Power Present = Shorted Low Voltage Wire
- No Power ⇒ Check for 24VAC between "C" and the now empty subbase terminal.
- Power Present = Bad Subbase
3. Check Control Board
- Confirm that there is no fault code on the control board.
- Cycle high voltage power at the air handler just to make sure there was no lockout.
- Remove the two low voltage wires at the motor plug (should be Red and White).
- Blower Continues to Run = Bad X-13 Motor
- Blower Stops = Bad Control Board
- Especially in counter-flow applications, the control board is extremely susceptible to water damage from condensate overflow.
- ► Look for water in the base of the air handler, or obvious signs of water damage.