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Air Conditioner Electronic expansion valve: What It Does and Signs It's Failing

A motor-driven metering valve, usually in the outdoor unit, that controls how much refrigerant flows into the coil that's doing the cooling or heating. Working alongside the variable-speed compressor, it keeps the refrigerant flow matched to the load.

How it works

The board steps a small motor that moves a needle in the valve, opening or closing the passage based on temperature sensor readings. A coil clips over the valve body and can be replaced separately.

Signs it is failing

• Poor cooling or heating with clean filters and coils
• Ice on the outdoor or indoor coil
• Expansion valve coil codes
• High discharge temperature or low pressure codes

EEV codes and some temperature and pressure codes involve this valve. Its coil or wiring can also be at fault.

Can you replace it yourself?

There's nothing to service yourself beyond a power reset. The valve body is brazed into the refrigerant lines, so replacing it opens the refrigerant circuit, and in the US that legally needs an EPA Section 608-certified technician. The coil can be changed without opening the lines, but it's wired into the outdoor unit's electrical compartment, so that's tech work too.

Buying the right part

The tech will order the valve or coil to match your outdoor unit model.

Error codes linked to the electronic expansion valve

• U0Low refrigerant or restricted refrigerant flowDaikin
• F3Compressor discharge temperature too highDaikin
• A1Discharge temperature too highFujitsu
• A3Compressor temperature too highFujitsu
• A5Low pressure errorFujitsu
• P8Pipe temperature errorMitsubishi Electric
• PLRefrigerant circuit abnormalMitsubishi Electric
• E422Refrigerant flow blockedSamsung

Last reviewed 2026-10-19.