York Package Heat Pump: BHX

Re: Fan Runs Continuous - Heating

The customer reports that the indoor blower runs continuous with no call for heating.

► The heater board in this unit has a 3-Limit Trip Lockout which disables the heaters and runs the fan continuous.

CHECKOUT:

1. Check the Thermostat

• Set the thermostat system switch to "Off" and the fan switch to "Auto".

2. Check Low Voltage Power

• 24V Power
• Check for 24VAC between "R" and "C" on the low voltage wiring.
  • No Power = Blown Low Voltage Fuse or Bad Transformer
• Call for Fan
• Check for 24VAC between "G" and "C" on the low voltage wiring.
  • No Power + Blower Running ⇒ Check Call for Heat
  • Power Present →  Step 3. Check Control Wiring
• Call for Heat
• Check for 24VAC between "W" and "C" on the low voltage wiring.
  • Power Present + Blower Running →  Step 3. Check Control Wiring
  • No Power + Blower Running → Step 4. Check for Limit Trip

3. Check Control Wiring

• Remove the thermostat from the subbase.
• Re-check Call for Fan and Call for Heat
  • 24VAC Still Present = Shorted Control Wire
  • 24VAC Goes Away = Bad Thermostat

4. Check for Limit Trip

• Check for 24VAC across the coil of K7 relay.
  • Power Present ⇒ Reset high voltage power to the unit.
    • Power goes away and fan stops = 3-Limit Lockout.
    • Power Still Present ⇒ Check for Open Limit Switch
  • No Power + Blower Running ⇒ Check for 24VAC between "Wht" at Pin#13 of the ECM and Gnd.
    • Power Present = Stuck K7 relay.