DNQ - Flashing Code 2

Package Unit: DNQ

Re: Code 2

There are 2 control boards on this unit, a CFM Selector Board (CFMCB) which controls the variable speed blower motor and an Ignition Control Board (ICB). The ICB controls the inducer fan, spark ignition and gas valve.

► All heating diagnostics will be displayed on the ICB.

CODE 2 = Pressure switch "Open" with the inducer motor energized.

CHECKOUT:

1. Check Heating Sequence

• Energize a call for heat from the thermostat.
• Ensure that the inducer motor starts.
  • No Inducer + Code 2 → Step 2. Check Control Board
  • Inducer Starts + Code 2 → Step 4. Check Pressure Switch

2. Check Control Board

• Check for 24VAC between "W1" and "C" on the CFMCB.
• Check for 24VAC between "W' and "C" on the ICB.
  • No Power on "W1" = No Call for Heat
  • Power on "W1" + No Power on "W" = Bad CFMCB
• Check for 230VAC between Ignition Control Board [IND] terminal (BLK) and Compressor Contactor L2 (PRP).
  • Power Present → Step 3. Check Inducer
  • No Power = Bad Ignition Control Board

3. Check Inducer

• Check the temperature of the inducer motor.
• Use an Amp Probe to check the amperage of the inducer motor.
  • 230V Power + Hot Motor + No Amperage = Off on Overload ⇒Turn off power to the unit, allow motor to cool, then recheck.
  • 230V Power + Cool Motor + No Amperage = Bad Inducer Motor
  • 230V Power + Amperage + Not Running = Bad Inducer Motor or Item Stuck in Inducer Wheel ⇒ Remove Inducer Assembly & Check Wheel

4. Check Pressure Switch

• Check for 24VAC between "C" of the CFMCB and 245/PRP on the pressure switch.
  • Power + Code 2 = Bad Ignition Control Board
  • No Power = Open Pressure Switch
    • Use a pressure gauge to check the negative pressure from the inducer.
      • Adequate Negative Pressure = Bad Pressure Switch
      • No or Low Negative Pressure ⇒ Remove the inducer assembly, check the condition of the blower wheel and look for a Clogged Pressure Port