CODE 13
Fraser-Johnston
Limit Circuit Lockout
LED flashes one short and three long blinks; blower runs but burners do not light.
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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
Open high limit or rollout switch, Loose connection in limit circuit, Faulty limit switch, Overheating due to airflow restriction
How to Fix / Troubleshooting
Safety first: Turn off power and allow furnace to cool before touching limit switches.
- Check all limit switches: Using the wiring diagram, locate the high limit and rollout switches wired in series. With power off, check continuity across each. Any open switch when the furnace is cool indicates a tripped or failed device.
- Reset manual rollout switches: If equipped with reset buttons, press gently until they click. If they trip again, stop and call a professional.
- Correct airflow issues: Replace the filter, open registers, and inspect the blower wheel for dirt buildup.
- Reset lockout: Cycle power to clear the code. If Code 13 returns, have a technician inspect for heat exchanger or combustion issues.
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Repair Difficulty
Hard
4/5
Required Part
Rollout Switch
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