Daikin Air Conditioner

Daikin AC P4 error

Inverter heat-sink temperature sensor fault

Needs a technicianCross-checked from 2+ sources

Try a reset once. If it comes back, a trained technician should repair it.

What it means

The control board is getting a wrong reading, or no reading, from the inverter heat-sink temperature sensor. Usually the sensor, its wire or its plug is loose, damaged or has failed.

Common causes

Loose or rusted sensor plug on the control board
Sensor wire cut, pinched or bitten by rats
Sensor has failed (open or short circuit)
Less often, a fault on the control board

Try this at home first

Tick each step as you go

Switch off at the wall socket or MCB for 5 minutes, then restart
If the code does not come back, no further action is needed
Look for any visible wire damage from outside — do not open covers

When to call a technician

If the code returns after a reset, a technician needs to test and usually replace the sensor. It is a common, low-cost repair.

Safety first

Always switch off at the wall socket or MCB before touching any part. Do not open the outdoor unit, control boards or gas pipes yourself — they carry high voltage and pressure.

Frequently asked questions

What does P4 mean on a Daikin Air Conditioner?

Inverter heat-sink temperature sensor fault. The control board is getting a wrong reading, or no reading, from the inverter heat-sink temperature sensor. Usually the sensor, its wire or its plug is loose, damaged or has failed.

Can I fix Daikin Air Conditioner error P4 myself?

You can try a reset first: Switch off at the wall socket or MCB for 5 minutes, then restart. If the code returns, call a technician.

Is it safe to keep using the Air Conditioner with P4?

Avoid repeated restarts; running with this fault can cause more damage.

Other Daikin AC codes

H9 Outdoor air temperature sensor fault J3 Compressor discharge temperature sensor fault J6 Outdoor coil (condenser) temperature sensor fault L3 Inverter board / power module protection L4 Inverter board / power module protection L5 Inverter board / power module protection U0 Low gas / refrigerant leak or blockage U2 Power supply voltage problem U4 Communication error (indoor ↔ outdoor unit) UA Indoor/outdoor mismatch or wrong wiring

All Daikin Air Conditioner error codes

Same code on other brands

P4 Inverter board / power module protection / Power supply voltage problemVoltas AC P4 Power supply voltage problemBlue Star AC

Sources

We write every explanation in our own words from these references.

Last checked: 2026-10-20