Denso Air Conditioner Error Code FT

The FT code indicates a defect detected on the freeze protection thermistor circuit connected to connector J102. The system has found either a short circuit or an open circuit on this sensor. The freeze protection thermistor monitors evaporator coil temperature to prevent ice formation, and the unit will not operate normally until the fault is corrected.

Operating the unit with an FT fault is not recommended. The freeze protection thermistor is a safety component that prevents the evaporator coil from icing over. Without a functioning sensor, the system cannot detect coil freeze conditions, which can lead to reduced airflow, compressor damage, or refrigerant issues over time.

If the issue is simply a loose connector, there may be no parts cost involved, only a service call fee which typically ranges from $75 to $150 depending on your location. If the freeze protection thermistor needs replacement, parts and labor combined generally range from $100 to $300. Wiring harness repairs or control board replacement would fall on the higher end of that range or beyond.

Start by disconnecting and firmly reconnecting the freeze protection thermistor at the J102 connector, as a loose or corroded connection is the most common cause. If the error returns, inspect the wiring harness between the thermistor and J102 for damage. If the wiring is intact and the connector is secure, the thermistor itself will need to be replaced.

A power reset may temporarily clear the FT code, but the fault will return if the underlying problem with the thermistor or its wiring has not been corrected. The recommended first step is to disconnect and reconnect the thermistor before cycling power, as this addresses the most common cause. A persistent fault after reconnection and reset indicates the thermistor needs replacement.