York Gas Furnace: PUDD
Re: Burners Fire then Shut Off
The furnace goes through a normal ignition sequence, but several seconds after ignition the burners shut off.
Qty |
Possible Causes (From Most to Least Likely): |
2 |
Dirty flame sensor |
|
Bad Ignition Control |
|
Incomplete Ignition |
|
Pressure Switch Opening |
|
Thermostat Short-Cycling |
CHECKOUT:
1. Check Power to Ignition Control
- Check for 24VAC power between "TH" or "24V" on the ignition control and "C" on the terminal block.
- Monitor power through the ignition sequence.
- Power drops out when burners shut off = Pressure Switch Opening or Thermostat Short-Cycling
- Power stays on but burners shut off --> Step 2. Check Ignition
2. Check Ignition
- Visually inspect the burners during ignition.
- Burners should light with little or no delay from the glow plug to the flame sensor.
- Make sure flame sensor comes in good contact with the flame.
- Any delay or burners not igniting = Clogged Burners
- Burners light properly --> Step 3. Check Flame Sensor
3. Check Flame Sensor
- On the multi-meter:
- Switch the test leads to "COM" and "mA".
- Set the meter on DC 200รน.
- Disconnect the wire from the flame sensor.
- Place one meter lead on the flame sensor terminal and the other on the flame sensor wire.
- Check the reading when the burners ignite.
- Minimum acceptable reading = 1 MicroAmp
- Low Reading --> Clean Flame Sensor & Re-check
- Normal Reading (2 to 6 mA) but Shuts Off = Bad Ignition Control
- MOVE SENSOR LEADS BACK TO "COM" and "V" BEFORE PROCEEDING!