Error code reference
Lennox Air Conditioner Error Code E440
Heat sink temperature is approaching limit (inverter code 13); compressor speed automatically slows to reduce…
Heat sink temperature is approaching limit (inverter code 13); compressor speed automatically slows to reduce heat sink temperature.
First step from the service manual
Tighten screws that hold the heat sink to the inverter control board. Wait 5 minutes to allow capacitor to discharge before checking screws.
The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.
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- Step-by-step tests with expected resistance, voltage, and continuity values
- Wiring diagram references and connector pinouts from the OEM service manual
- Verified part numbers when replacement is required
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