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Error code reference

Samsung Heat Pump Error Code E405

CT low current error

Samsung codesSamsung heat pump codes
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What the E405 error code actually means

Your Samsung heat pump has detected that the compressor is not drawing enough electrical current, which suggests either the compressor is not running properly or the sensor that measures its current has a problem. The system has been watching this condition for over 10 minutes before displaying this error. A technician will need to inspect the sensor and its wiring to determine whether the compressor or the measurement components are at fault.

Diagnostic procedure

The full E405 procedure

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1
First diagnostic step
Check CT sensor connector resistance; verify CT value is 0 when compressor is stopped.
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Most common causes of E405

Ranked by how often they cause this code
  1. 1Loose or corroded CT sensor connector
  2. 2Faulty CT sensor
  3. 3Damaged wiring harness between CT sensor and control board
  4. 4Compressor not starting or running under load
  5. 5Faulty main control PCB

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Questions people ask about E405

What does E405 mean on a Samsung heat pump?
E405 is a CT low current error indicating that the current transformer sensor monitoring the compressor has read below 4 amperes for more than 10 consecutive minutes. This tells the control board that the compressor is either not running at the expected load or that the CT sensor circuit has a fault. The system uses this threshold as a safety and diagnostic check to detect compressor or sensor problems early.
Is it safe to run my heat pump while the E405 code is active?
Continuing to operate the unit with an active E405 fault is not recommended. If the compressor is genuinely not running or is running improperly, forcing continued operation could cause additional damage to the compressor or refrigerant circuit. It is best to stop the unit and have it inspected before resuming normal use.
How much does it cost to repair a Samsung heat pump E405 error?
Repair costs vary depending on the root cause. If only the CT sensor connector needs cleaning or reseating, the cost may be limited to a service call fee, typically in the range of $75 to $150. Replacing a CT sensor generally runs $100 to $300 including parts and labor. If the compressor itself has failed, repair or replacement costs can range from $600 to well over $1,500 depending on the unit and parts availability.
Can I fix the E405 error myself?
Some steps are DIY-friendly, such as inspecting the CT sensor connector for corrosion or a loose fit and reseating it securely. However, diagnosing whether the fault lies in the CT sensor, wiring harness, compressor, or control board requires measuring resistance values and interpreting CT readings, which generally calls for a qualified technician. Working inside a heat pump also involves high-voltage components, so caution is essential.
Will resetting the heat pump clear the E405 error?
A power reset may temporarily clear the E405 code, but if the underlying issue, such as a faulty CT sensor, poor connector, or compressor problem, is still present, the error will return once the system runs long enough to detect the low current condition again. A reset is useful for confirming whether the fault is intermittent, but it does not repair the cause.

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