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Error code reference

Samsung Air Conditioner Error Code E151

Error due to opened EEV of indoor unit (2nd detection)

Samsung codesSamsung air conditioner codes

Error due to opened EEV of indoor unit (2nd detection) - refrigerant leaking into stopped indoor unit.

First step from the service manual

Check if EEV wire is connected to PCB.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What E151 means on a Samsung air conditioner

Samsung E151 is a second-detection fault triggered when the Electronic Expansion Valve (EEV) of an indoor unit is found to be in an unexpectedly open position while that indoor unit is stopped. The EEV is a precision refrigerant metering component controlled by a stepper motor, and it should close fully when its associated indoor unit is not operating. When the system detects that refrigerant is migrating into a stopped indoor unit through an open or partially open EEV, it logs this as E151. The "2nd detection" designation means the system has confirmed the condition across two consecutive detection cycles, ruling out a transient or spurious reading.

The core concern with this fault is refrigerant flooding into an idle indoor unit. When liquid refrigerant accumulates in the indoor coil or around the compressor during off cycles, it can cause compressor slugging or oil dilution on startup, leading to mechanical damage. The EEV may fail to close due to a wiring fault, a failed stepper motor coil, a stuck valve body, or a loss of communication between the PCB and the valve actuator. Because the valve position is driven by pulse signals from the indoor PCB, any break or short in the wiring harness between the PCB and EEV can cause the valve to default to or remain in an open state.

The first diagnostic step is to inspect the EEV wiring harness connection at the indoor PCB. A loose, corroded, or damaged connector can interrupt the stepper motor drive signal, preventing the valve from receiving the close command. If the wiring checks out, the EEV coil resistance should be measured and the valve body inspected for mechanical failure. Refrigerant leak testing of the system may also be warranted if the valve is confirmed functional, as abnormal pressure differentials can force refrigerant migration past a marginally sealing EEV.

Source: manufacturer service documentation.

Common causes of E151

  1. 01

    Loose or disconnected EEV wiring at the PCB

    Wiring / connection

    The harness connector between the indoor PCB and the EEV stepper motor may be loose, improperly seated, or have spread terminals. This is the first item to check and is a common root cause because the valve cannot receive close commands without a solid electrical connection.

  2. 02

    Failed EEV stepper motor coil

    Part replacement

    The stepper motor that drives the EEV open and closed has multiple coil windings that can fail due to heat cycling or age. A failed coil will prevent the valve from responding to position commands, leaving it stuck in its last position or defaulting open.

  3. 03

    Mechanically stuck or fouled EEV valve body

    Part replacement

    Debris, refrigerant oil contamination, or internal corrosion can physically prevent the valve needle from seating fully. This can occur after a compressor burnout or in systems with moisture contamination in the refrigerant circuit.

  4. 04

    Damaged EEV wiring harness

    Part replacement

    The wiring between the PCB and EEV can develop shorts or open circuits due to pinching, rodent damage, or repeated flexing during installation. Inspect the full harness run for visible damage and test continuity on each conductor.

  5. 05

    Indoor PCB fault

    Part replacement

    If the PCB itself cannot generate the correct stepper motor drive signals, the EEV will not close regardless of the valve or wiring condition. This is less common but should be considered after the EEV and harness have been confirmed functional.

See the test procedure for each cause

Frequently asked questions about E151

What does E151 mean on a Samsung air conditioner?
E151 indicates that the Electronic Expansion Valve (EEV) in one of the indoor units has been detected in an open state while that unit is not running, allowing refrigerant to flow into the stopped unit. This is a second-detection fault, meaning the system confirmed the condition over two detection cycles. It points to a wiring fault, a failed EEV stepper motor, or a mechanically stuck valve. The issue requires inspection by a qualified technician.
Can I fix E151 myself, or do I need a technician?
The first diagnostic step, checking that the EEV wiring harness is securely connected to the indoor PCB, is something a knowledgeable DIYer can do safely with the unit powered down. However, any further diagnosis involving refrigerant pressures, coil resistance measurements on the EEV, or component replacement should be performed by a licensed HVAC technician. Working on the refrigerant circuit requires proper certification and equipment.
Is it safe to keep running my air conditioner with an E151 error?
Continuing to operate the system with an active E151 fault is not recommended. Refrigerant migrating into a stopped indoor unit can flood the compressor on the next startup, potentially causing mechanical damage to the compressor. Shut the system down and have it inspected before resuming normal operation to avoid a more costly repair.
Will resetting the unit clear the E151 error code?
A power reset may temporarily clear the displayed fault, but if the underlying cause, such as a faulty EEV, damaged wiring, or a stuck valve body, has not been corrected, the error will return. Because E151 is a second-detection fault, the system has already confirmed the problem across multiple checks. Resetting without repairing the root cause risks compressor damage.
How much does it cost to repair an E151 error on a Samsung air conditioner?
Repair costs depend on the root cause. If the fix is simply reseating a loose EEV connector, the cost may be limited to a diagnostic service call fee, typically in the range of $75 to $150. If the EEV coil or valve body requires replacement, parts and labor can range from $200 to $600 or more depending on the unit model and local labor rates. If the indoor PCB is at fault, costs can be higher.

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