Low Pressure Drop

What it means

This code appears on Daikin air conditioners, most often on SkyAir ducted and cassette units fitted with a low pressure sensor or switch, and means the suction-side refrigerant pressure fell below the allowed limit. The unit stops the compressor to protect it; the usual causes are low refrigerant or a closed service valve. The same code can mean something else on other brands.

Models covered: Daikin split air conditioners and Daikin ducted/cassette (SkyAir) units, which share the same error code system; the code shows on the wired remote or via the wireless remote check function.

Related codes: U0E9A5F3

Symptoms4

• The compressor stops and E4 appears.
• Weak or no cooling before the code appears.
• Frost on the suction pipe or outdoor service valves at times.
• The unit runs briefly after a restart and then trips.

Possible causes5

• Low refrigerant charge from a leak at the joints, piping or coils.
• An outdoor service valve left closed after installation or service.
• Poor airflow over the indoor evaporator from dirty filters or a weak fan.
• An electronic expansion valve fault or a restriction in the circuit.
• A faulty low pressure sensor or switch, or its wiring.

How to diagnose5

1. Switch the unit off, clean the filters and confirm strong airflow from the indoor unit.
2. If the unit was recently installed or serviced, have the technician confirm the service valves are fully open.
3. The technician measures pressures and pipe temperatures and compares them with Daikin specifications.
4. The technician searches for leaks with an electronic detector or soap solution on the joints.
5. The technician checks the electronic expansion valve and the low pressure sensor and their wiring.

How to fix5

1. Clean the filters and evaporator if poor airflow is the cause.
2. Open the service valves fully if they are partly closed.
3. A licensed technician repairs the leak, evacuates the system and recharges to the nameplate amount.
4. Replace the electronic expansion valve or low pressure sensor if proven faulty.
5. Run the unit, check pressures and cooling, and confirm the code does not return.

Repair cost

In Saudi riyals; the highlighted part is the expected range for this fault.

Opening a valve or cleaning filters is cheap, while a leak repair with recharge or a new expansion valve raises the cost.

Prices are rough estimates including the part and the technician’s fee, and vary with brand, model and part source.
Prices last updated: September 2026

Frequently asked questions