Lennox Air Conditioner Error Code E438

E438 indicates that the inverter has detected a PFC (Power Factor Correction) over current condition, recorded internally as inverter code 73. This fault is triggered by one of three conditions: high refrigerant pressure, a high system load, or outdoor fan failure. The inverter shuts down to protect its internal power components from damage caused by excessive current. Checking for high pressure trips or additional alert codes on the thermostat and outdoor control is the recommended first diagnostic step.

No, the unit should not be forced to continue operating while E438 is active. The inverter has shut down specifically to prevent damage to internal power components such as transistors and capacitors. Running the system without resolving the underlying cause, whether a failed outdoor fan, high pressure condition, or inverter issue, risks causing more extensive and costly damage to the inverter module or compressor.

Repair costs vary significantly depending on the root cause. A condenser coil cleaning or outdoor fan capacitor replacement might cost in the range of $100 to $300. A failed outdoor fan motor typically runs between $200 and $500 including labor. If the inverter module itself has failed, replacement costs can range from $600 to over $1,500 depending on the unit model and local labor rates. Getting a diagnostic visit from a certified technician is the best way to obtain an accurate estimate.

Some aspects of diagnosing E438 are accessible to a knowledgeable DIYer, such as inspecting the outdoor fan for rotation, checking for a dirty condenser coil, and reviewing any additional fault codes on the thermostat. However, refrigerant pressure diagnosis and inverter board evaluation require certified HVAC technicians with proper tools and certifications. Attempting to work on the refrigerant circuit without proper credentials is both illegal and dangerous.

A reset may temporarily clear the fault and allow the unit to restart, but it will not resolve the underlying cause. If the outdoor fan is failed, the condenser coil is blocked, or a high pressure condition exists, the E438 fault will return, often quickly. Repeated faults without addressing the root cause can lead to progressive damage to the inverter. Always diagnose and correct the cause before relying on a reset.