Denso Air Conditioner Error Code DF

The DF code indicates a freezing abnormality has been detected at the evaporator inlet. The inlet air thermistor measured a temperature at or below 26.5°F (-3°C) while the compressor was running. The system waits 5 minutes after compressor startup before checking for this fault to avoid false triggers during normal pull-down. The unit shuts down to protect the evaporator coil and compressor from ice-related damage.

No, continued operation with an active DF fault is not recommended. A freezing evaporator can lead to complete airflow blockage as ice builds up, and if liquid refrigerant is drawn back into the compressor, it can cause serious compressor damage. Power the unit off and allow it to defrost before investigating the cause.

A power reset may clear the displayed fault code temporarily, but the DF code will return if the underlying cause has not been corrected. The 5-minute detection delay after compressor startup means you may get a brief period of operation before the fault reappears. Address the root cause, such as restricted airflow or a faulty thermistor, before relying on a reset as a solution.

Some causes of the DF code are DIY-friendly. Start by turning off the unit and allowing any ice on the evaporator to fully thaw, then check and replace the air filter if it is dirty. If the error returns after the filter is cleaned and airflow is confirmed to be unobstructed, the issue likely involves refrigerant charge or a faulty thermistor, both of which require a qualified technician.

Repair costs depend on the root cause. Replacing an air filter is a low-cost fix, typically in the range of $10 to $30 for the part. A thermistor replacement by a technician may cost $75 to $200 in parts and labor. If the fault is due to a refrigerant leak, diagnosis, leak repair, and recharge can range from $150 to $500 or more depending on the extent of the problem.