44
Ducane
Auxiliary Limit Open
Code 44, secondary limit or auxiliary limit open on condensing Ducane furnace
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Clogged secondary heat exchanger, Blocked condensate drain, Restricted airflow across A-coil, Failed auxiliary limit switch
How to Fix / Troubleshooting
Safety first: Turn off power and gas before servicing internal components.
- Step 1 – Check filter and coil: Replace dirty filters and inspect the evaporator coil for heavy dirt buildup.
- Step 2 – Clear condensate system: Clean the condensate trap and drain line. Ensure proper slope and no kinks.
- Step 3 – Inspect auxiliary limit: Locate the auxiliary limit on or near the secondary heat exchanger. Some are manual reset; press reset if present. If it trips again, stop using the furnace and call a professional.
- Step 4 – Professional cleaning: A technician may need to chemically clean the secondary heat exchanger and verify temperature rise.
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Repair Difficulty
Hard
4/5
Required Part
Auxiliary Limit Switch
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