Lennox Air Conditioner Error Code E433

E433 means the inverter control board has detected a peak phase current greater than 28 amperes in the compressor circuit, which is logged as inverter fault code 29. This is an over-current protection shutdown designed to protect the compressor and inverter components from damage. The system will not run until the underlying cause is resolved.

No. The unit should not be operated repeatedly while displaying E433. The over-current condition that triggered this fault can cause overheating and permanent damage to the compressor motor windings and inverter drive components if the root cause is not addressed. Leave the system off until a technician has diagnosed the problem.

Start by measuring supply voltage at the outdoor unit disconnect under load to rule out low voltage as the cause. Next, check refrigerant pressures using manifold gauges to confirm the system is properly charged. If both check out, use a multimeter to measure compressor winding resistance across all three phases and a megohmmeter to test winding insulation to ground. If the compressor tests good, the inverter board is likely responsible for the fault.

Disconnecting power to the outdoor unit and restarting it is the recommended first step and may clear the fault if the cause was a transient electrical event. However, if a mechanical or electrical fault is present within the compressor, inverter board, or power supply, the E433 code will return after the reset and the unit may shut down again quickly. A reset alone is not a repair.

Repair costs vary significantly depending on the root cause. If the fix involves a refrigerant charge or an electrical correction at the service panel, costs are generally lower, typically in the range of $150 to $400. If the inverter board requires replacement, expect costs of $500 to $1,200 or more depending on the model. Compressor replacement is the most expensive outcome, often ranging from $1,200 to $2,500 or higher including labor.