Package Unit: DNQ
Re: Won't Ignite / Code 5
The sparker ignites the pilot but never senses flame to energize the main gas valve, and the control board shows no fault codes.
- The DNQ package unit has two control boards, an Ignition Control Board (ICB) and a CFM Control Board (CFMCB).
- The thermostat connections are on the CFM Board which controls the cooling and indoor blower.
- The CFM board sends heating outputs to the Ignition Control Board for all heating functions.
CODE 5 = 5 Consecutive Loss of Flame - The flame sensor detects the presence of pilot flame. Flame is not detected in 5 consecutive ignition attempts.
Qty |
Possible Causes: |
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Dirty Flame Sensor |
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Clogged Pilot Orifice |
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Low Gas Pressure |
1 |
Bad Ignition Control Board (ICB) |
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Bad Gas Valve |
CHECKOUT:
1. Check Gas Pressure
- Use a gas pressure gauge to check the inlet gas pressure at the gas valve.
- Low Inlet Gas Pressure = Gas Supply Problem
2. Check Ignition Sequence
- Energize a call for heat from the thermostat, or place a jumper between "R" and "W" on the CFM Board.
- Ensure that the inducer motor starts and the ICB sparks at the pilot.
- No Inducer or No Spark ⇒ Check board for fault indications.
- Confirm that the inlet gas pressure maintains at the proper pressure.
- Inlet Gas Pressure Drops = Gas Supply Problems
- Visually inspect the pilot to see if the pilot lights.
- Pilot Doesn't Light ⇒ Check for 24VAC between "C" and "P" at the gas valve.
- No Voltage = Bad ICB
- Voltage + No Pilot = Bad Gas Valve or Clogged Pilot Orfice
- Visually inspect the pilot flame to make sure it comes into steady contact with the Flame Sensor.
- No Contact = Low Pilot Pressure or Dirty Pilot Orifice
- Contact but No Main Flame ⇒ Check for 24VAC between "C" and "M" at the gas valve.
- Power + No Flame = Bad Gas Valve
- No Power = Dirty Flame Sensor or Bad ICB ⇒ Clean the Flame Sensor and Recheck