Samsung Air Conditioner Error E121

⚡ Quick Answer: The Samsung Air Conditioner error E121 signifies a communication failure between the indoor and outdoor units, primarily due to a defective or malfunc... ✅ DIY Fixable

What Does Error E121 Mean?

The Samsung Air Conditioner error E121 signifies a communication failure between the indoor and outdoor units, primarily due to a defective or malfunctioning room temperature sensor. This error prevents the unit from cooling effectively and may lead to the thermostat being unable to accurately read the room temperature, resulting in the display of the E121 error code on the indoor unit panel.

Common Symptoms:

  • Error code E121 displayed on indoor unit panel
  • Air conditioner stops cooling or won’t start
  • Thermostat unable to read room temperature

Possible Causes

  • Defective or shorted/open room temperature sensor (indoor temp sensor) (high)
  • Sensor connection fault between room sensor and control board (medium)

How to Fix Error E121

DIY Fix Basic checks and reset

  1. Turn off the unit and disconnect power for a few minutes
  2. Ensure power supply is stable and securely connected
  3. Restart the unit to see if the error clears

Technician Only Sensor inspection and replacement

  1. Access indoor unit and test the room temperature sensor for open or short circuit using appropriate diagnostic tools
  2. Inspect wiring harness and connectors between sensor and control board for damage or corrosion
  3. Replace defective room temp sensor or repair wiring as needed

Parts needed: Room temperature sensor (indoor temp thermistor), Indoor wiring harness/connectors

🛑 When to Call a Pro:
  • If basic power reset doesn’t clear error
  • If sensor wiring or electrical diagnostics are needed
  • If error persists after simple checks

Next step

Choose the next step for E121

Confirm the diagnosis before ordering. An error code can identify the system involved, but it does not prove that a specific part has failed.

Based on diagnostic data

Most relevant component to inspect

Temperature Sensor

Monitors the internal temperature to ensure correct operation and prevent overheating.

Typical part-only price
$15 - $35
DIY difficulty
Easy
Estimated time
15-30 mins
Where can I find the model number?

Check the rating label around the door, lid, frame, rear panel, or inside the appliance cabinet. Use the complete model number, including suffixes.

Find a part that fits my model

Verify the complete model and part number on the retailer's compatibility page before ordering.

Other parts options

Check related components first; use model search as a fallback.

Possible related component

Wiring Harness

Connects controls, sensors, motors, and other electrical components inside the appliance.

$20 - $120 · Medium · 30-90 mins

Check fit & price
Model number required

Model-compatible Air Conditioner parts

Enter the complete model number to browse compatible replacement parts. This is a model-based parts search, not a diagnosis that a specific component failed.

Find a part that fits my model

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Optional routine care

Maintenance supplies

These products support cleaning or routine upkeep. They are separate from the possible repair components above and are not claimed to fix this error code or symptom.

Maintenance supply

Air Conditioner Fin Cleaner

For routine cleaning of accessible coil fins when permitted by the manufacturer. Disconnect power and follow product and appliance instructions.

View maintenance supply
Maintenance supply

Model-Compatible Washable AC Filter

A reusable filter option only where the appliance supports one. Match the full model, dimensions, and filter specification.

Compatibility check required: use the complete appliance model and compare the existing filter, bag, or specification before ordering.

Find one that fits my model

Affiliate disclosure: As an Amazon Associate I earn from qualifying purchases. Recommendations are based on routine-care relevance, not commission rate.

Technical Specifications

wattage 2000W
component Control Board
resistance 5-10 ohms
part_number DA92-00338A
voltage_rating 220V AC

Common Questions

What does E121 error mean on Samsung Air Conditioner?

E121 indicates a communication failure between indoor and outdoor units due to a faulty room temperature sensor.

Can I fix Samsung Air Conditioner E121 error myself?

Yes, you can try basic checks like power resets and ensuring stable connections before calling for repair.

How much does it cost to fix E121 error?

Repair costs vary; sensor replacement is typically low cost, but service calls may add to the total.

When should I call a technician for E121?

Call a technician if the error persists after resets or if wiring and electrical diagnostics are needed.

Sources & References

Data last verified: 2026-07-22

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