Daikin Air Conditioner Error Code F6

The F6 code on a Daikin air conditioner means the system has detected a refrigerant overcharge condition during its check operation. The unit reaches this conclusion by comparing the outdoor air thermistor reading against the heat exchanger deicer thermistor reading. When those values fall outside the expected relationship, the system flags F6 to prevent damage from operating with excess refrigerant. Note that a faulty or loose thermistor can also trigger this code even if the refrigerant charge is actually correct.

A power reset may temporarily clear the F6 code, but the fault will return during the next check operation if the underlying cause has not been resolved. If a thermistor is loose or faulty, or if the refrigerant charge is genuinely incorrect, the system will detect the same out-of-range temperature relationship and re-trigger the error. A reset alone is not a fix and should only be used after the root cause has been identified and corrected.

Repair costs vary depending on the root cause. If only a thermistor needs repositioning or replacement, costs are generally in the range of 80 to 200 dollars including labor. If the system requires refrigerant recovery and recharge due to an actual overcharge, costs typically range from 150 to 400 dollars or more depending on refrigerant type, the amount involved, and local labor rates. A diagnostic service call is usually needed first to determine the exact cause.

The first step, checking that both the outdoor air thermistor and the deicer thermistor are correctly mounted and making good contact, is something a knowledgeable DIYer can inspect visually. However, if the thermistors appear properly seated and the fault persists, verifying or adjusting the refrigerant charge requires EPA certification and professional equipment. Any work involving refrigerant must be performed by a licensed technician.

Operating the unit continuously with an F6 code is not recommended. If the refrigerant is genuinely overcharged, running the system can result in elevated pressures that stress the compressor and refrigerant circuit components, potentially causing serious damage. The unit should remain off until a technician has confirmed whether the issue is a sensor problem or an actual refrigerant overcharge.