Error code reference

Lennox Air Conditioner Error Code E443

Incorrect appliance unit size code selected.

Lennox codes Lennox air conditioner codes

Incorrect appliance unit size code selected.

First step from the service manual

Check for proper configuring of unit size codes. If replacing inverter, verify inverter model matches unit size. Remove thermostat from the system while applying power and reprogramming.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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Get the full diagnostic procedure for E443.

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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E443 on my Lennox Air Conditioner

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Incorrect appliance unit size code selected

From Service Manual 873134, p.26:

1.Check for proper configuring of unit size codes. If replacing inverter, verify inverter model matches unit size. Remove thermostat from the system while applying power and reprogramming.

2.Measure line voltage at the power cord terminal block. Expected: 120 VAC (L1 to neutral) or 208 to 240 VAC between L1 and L2 under load.

3.Inspect the cord strain relief and terminal block screws for signs of arcing or heat discoloration. Loose connections here mimic an intermittent power failure to the control board.

Part W10911048

Power cord assembly

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First step from the service manual

Get the full diagnostic procedure for E443.

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