Lennox OF23Q3/4-105 - User Manual

Questions and Answers

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Carrie WoodAug 16, 2025
What to do if Lennox OF23Q3/4-105 burner starts and locks out?
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  april49Aug 16, 2025
  If your Lennox Furnace burner starts and fires but then locks out on safety, it could be due to several reasons related to air and combustion. Check for an unbalanced fire and replace the nozzle if necessary. If there's too much air, reduce the combustion air and check combustion. Conversely, if there's too little air, increase the combustion air and check combustion. Excessive draft can be corrected by adjusting the barometric damper. Insufficient draft or a restriction should be corrected or removed. A dirty cad cell face should be cleaned, and a faulty cad cell should be replaced. Lastly, a defective primary control circuit may require replacement of the primary control.
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jason05Aug 25, 2025
What to do if Lennox OF23Q3/4-105 runs continuously?
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  David MartinAug 25, 2025
  If your Lennox Furnace burner runs continuously and produces too much heat, several thermostat-related issues may be the cause. Check for shorted or welded thermostat contacts and repair or replace the thermostat if needed. If the thermostat bimetal is stuck, clear any obstruction or replace the thermostat. Ensure the thermostat is level. Repair any shorted thermostat wires or replace them. If the thermostat is out of calibration, replace it. Correct any cold drafts affecting the thermostat or relocate it. Finally, a defective primary control may also cause this issue, requiring replacement.
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Steven MorrisonOct 31, 2025
How to fix Lennox Furnace burner that fails to start?
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  Lori DuncanOct 31, 2025
  If your Lennox Furnace burner fails to start, there are several potential causes. First, ensure the thermostat is set to HEAT and not OFF or COOL. Also, make sure the thermostat is set to a sufficiently high temperature. Other possible causes include a tripped burner motor overload (push the reset button), a tripped primary control (reset it), or a tripped auxiliary limit switch (reset it). Check for open switches (close them), blown fuses or tripped circuit breakers (replace/reset), and broken/loose thermostat wires (repair/replace). Also, check for loose thermostat screw connections (tighten them), dirty thermostat contacts (clean them), or a thermostat that isn't level (level it). If the thermostat is faulty, replace it. Shorted flame detector leads should be separated, and any false li...
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christopher26Nov 7, 2025
Why Lennox OF23Q3/4-105 burner starts, but there is no flame?
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  Charles PatrickNov 7, 2025
  If your Lennox Furnace burner starts but no flame is established, several issues could be the cause. First, ensure there is oil in the tank and fill it if necessary. If there's water in the oil tank exceeding 1 inch, pump or drain the water. Check that the tank shut-off valve is open. A plugged oil line filter requires replacement of the filter cartridges. Repair or replace any kinks or restrictions in the oil line. Locate and correct any air leaks in the oil supply line. If the pump is frozen, replace it. Replace a nozzle causing a poor or off-center spray with one of the same size, spray angle, and spray type. Clean fouled or shorted electrode leads. Clean eroded electrode tips and reset the gap to 5/32 inches. Finally, check the voltage at the power source if low line voltage is suspect...