HVAC Code Lookup

Daikin Mini-Split Code L4

Soft lockout

Radiation fin temperature rise. With the compressor running, the inverter heat sink got too hot (about 185 to 221F depending on class) and the unit stopped.

Manual wording: “L4 Radiation fin temperature rise”

Documented for: RKS/RXS pair outdoor units, FTXM-W/V outdoor units, RMXS multi-split outdoor

Likely causes, most common first

  1. Defective outdoor fan motor
  2. Short circuit (hot air recirculating into the outdoor unit)
  3. Defective radiation fin thermistor
  4. Disconnection of connector
  5. Defective outdoor unit PCB
  6. Silicon grease not applied properly on the radiation fin after replacing the outdoor unit PCB

What you can safely check yourself

  • Check the outdoor unit is not enclosed, crowded or blowing its own hot air straight back into itself
  • Clear leaves, grass and debris from the outdoor coil and around the base
  • Turn the system off at the breaker or disconnect switch and back on once

When to call a technician

If airflow around the outdoor unit is good and L4 keeps coming back, the fan motor or the inverter heat sink assembly needs a technician.

A Daikin mini-split throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.

Sources

Other Daikin codes