York Air Handler: NAH
York Package Heat Pumps: BHH, BHQ, BHZ
Re: 031-01264-002 Control Board - Heaters Not Working
The control board in these units operates the indoor blower and electric heaters.
There is one on-board, line-voltage heater output and three DC Voltage heater outputs for DC Voltage heater relays.
► A commonly missed reason for the heaters not working is a Limit Lockout.
If the limit trips four times during a single heating cycle or if the limit stays tripped for more than 80 seconds, the board will enter a hard lockout and not allow the heaters to come on.
The lockout can only be reset by cycling power to the board.
The tricky part is that the board has no LED light to indicate that it is in lockout.
► If the board has 24V power on "W1" and "W2" but no DC Voltage output to the heat relays, cycle power to the board to reset a potential lockout and retry.
| Qty | Possible Causes (From Most to Least Likely): |
| Low Airflow (Limit Lockout) | |
| Motor Speed Set Too Low (Limit Lockout) | |
| Failing Blower Motor (Limit Lockout) | |
| Bad Limit (Limit Lockout) | |
| Bad Control Board | |
| Bad Relays | |
| Bad Heaters |