Daikin AC Error Code C4 — High Pressure Protection

What Does This Error Mean?

C4 on a Daikin AC means the high pressure sensor has detected that refrigerant pressure has exceeded the safe limit and the system has shut down to protect the compressor. This is a protective shutdown, not a component failure in itself. The most common causes are a blocked condenser, failed outdoor fan, or refrigerant overcharge.

Affected Models

Daikin FTKF Series
Daikin FTKG Series
Daikin ATKF Series
Daikin Inverter Split AC (all models)
Daikin 1 Ton / 1.5 Ton / 2 Ton Inverter

Common Causes

Outdoor condenser coil blocked with dust, dirt, or cottonwood seeds
Outdoor fan motor failed — heat builds up around the condenser
Outdoor unit airflow obstructed by objects, vegetation, or walls too close
Refrigerant overcharged — too much refrigerant causes excessive pressure
Expansion valve stuck or restricted
Very high outdoor ambient temperature exceeding unit design limits

How to Fix It

Switch off the AC and inspect the outdoor unit immediately.

Check for airflow blockages on all sides and the top. Minimum clearances for Daikin outdoor units are typically 30 cm on the sides and 1 metre above.
Clean the outdoor condenser coil if visibly dirty.

With power off, gently rinse the condenser fins with a garden hose at low pressure. Work from inside the unit outward through the fins to push debris out rather than in deeper.
Verify the outdoor fan is spinning during operation.

Restart and watch the outdoor unit through the top grille. If the fan is not spinning, switch off immediately and call a technician — a non-spinning outdoor fan will cause C4 every time.
Allow 30 minutes for the system to cool before restarting after a C4 trip.

Refrigerant pressure takes time to drop after a high-pressure event. Restarting too quickly may trigger C4 again before conditions have normalised.

When to Call a Professional

If clearing the outdoor unit does not resolve C4, call a Daikin authorised technician. Refrigerant pressure issues require certified HVAC professionals with pressure gauges.

Frequently Asked Questions

How is Daikin C4 different from a regular high pressure error?

C4 on Daikin specifically indicates the high pressure sensor (not just the high pressure switch) detected over-pressure. The sensor provides continuous pressure data to the inverter board — when it reads above the safe threshold, C4 trips. Some Daikin models also have a separate mechanical high pressure switch that trips as a backup.

Can the Daikin C4 high pressure sensor itself fail?

Yes, though it is less common than the underlying pressure issue. A faulty sensor can trigger C4 even when actual system pressure is normal. A technician can connect a mechanical pressure gauge to the service ports to verify actual refrigerant pressure independently of the sensor.