Lennox Code 35
Pressure Limit Switch Error
What Lennox Code 35 Means
Pressure Limit Switch Error – Furnace does not ignite or shuts down during run
Common Causes
- Vent pipe blocked or kinked
- Pressure switch hose disconnected
- Furnace blower not running
- Heat exchanger cracked
- Pressure switch failure
First-Check: Step-by-Step Troubleshooting
- Inspect entire vent pipe for blockages
- Check pressure switch hose connection
- Listen for blower operation
- Test blower motor with multimeter
- Replace air filter
- Check for heat exchanger cracks
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