Lennox Air Conditioner Error Code E428

E428 means the inverter drive in the outdoor unit has detected a high main input current condition, which it logs as inverter code 22. The inverter shuts down to protect the compressor and itself from damage caused by excessive electrical current. This fault is most often triggered by high refrigerant pressure, a failed condenser fan, or an overcharged system.

No. The inverter shuts the system down when E428 occurs specifically to prevent compressor and drive board damage from overcurrent stress. Repeatedly forcing restarts without identifying and correcting the underlying cause can lead to compressor failure or inverter board damage, which are significantly more expensive repairs. Leave the unit off until the root cause has been addressed.

Repair costs vary widely depending on the cause. Cleaning a blocked condenser coil is typically the least expensive fix, often in the range of $100 to $250 for a service call. Replacing a condenser fan motor generally runs $200 to $500 including parts and labor. Correcting a refrigerant overcharge involves recovering and recharging the system, which can range from $150 to $400. Replacing a failed inverter module is the most costly scenario, often ranging from $500 to $1,200 or more depending on the model.

A homeowner can safely check that the outdoor condenser fan is spinning and that the outdoor unit is not blocked by debris, and can perform a power reset by shutting off the outdoor disconnect for several minutes. However, checking refrigerant pressures, diagnosing a failed fan motor, and correcting an overcharge all require a licensed HVAC technician with proper equipment. If the fault returns after a reset and the unit appears clear of obstructions, professional service is necessary.

Disconnecting power to the outdoor unit and restarting is the recommended first step and may clear the fault temporarily if the triggering condition was transient. However, if the underlying cause such as a failed condenser fan, high pressure, or overcharge is still present, the fault will return shortly after restart. A power reset should always be combined with a physical inspection of the outdoor unit before powering back on.