DNH/DNQ - Flashing Code 9

Package Unit: DNH / DNQ

Re: Code 9

• 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 9 = If either or both "Pilot" and "Main Gas" valve outputs are sensed to be off for more than 1 second when commanded to be on by the ICB, the control board shuts off all outputs and enters a hard lockout flashing "9" on the LED.

CHECKOUT:

1. Check Heating Sequence

• Energize a call for heat from the thermostat.
  • Reset the control if necessary by cycling power to the unit.
• Ensure that the Inducer Motor starts.
• After a 30-second Pre-Purge, the ICB should begin sparking while energizing the "PV" output (RED wire) to lite the pilot.
• When pilot flame is established, the ICB stops sparking and energizes the "MV" output (BLK wire).
• On 2-Stage models, the High-Fire is cycled by energizing the "H1" output (YEL wire).
• CODE 9 at any point → Step 2. Check Gas Valve

2. Check Gas Valve

• Make sure there is no call for Heat.
• Kill power to the unit by pulling the Service Disconnect.
• Take a Universal Electronic Ignition Gas Valve and temporarily connect to the system.
  • Don't remove the old valve or install a new one at this point.
  • Connect the RED wire to "PV".
  • Connect the BLK wire to "MV".
  • Connect the BLU wire to "C".
  • On 2-stage models, disconnect and leave the YEL wire un-hooked.
• Unit Still Locks-Out on CODE 9 ⇒ Suspect a Bad Control Board
• Unit Runs a Normal Ignition Attempt ⇒ Suspect a Bad Gas Valve