Indoor room temperature sensor fault
What it means
On Samsung air conditioners, E121 usually indicates a fault with the indoor room temperature sensor. The meaning can vary by model, so check the manual for your unit.
Symptoms3
- Room temperature does not settle at the set point.
- The unit stops and shows the code.
- Frequent on and off cycling for no clear reason.
Possible causes4
- Failed temperature sensor.
- Loose sensor plug.
- Moisture or corrosion at the connector.
- Indoor control board fault.
How to diagnose and fix3
- Cut power for two minutes, then restart.
- Have a technician test the sensor and reseat the plug.
- Replace the sensor if needed.
Repair cost
In Saudi riyals; the highlighted part is the expected range for this fault.
Usually a cheap sensor swap; cost rises if the board is the cause.
Prices are rough estimates including the part and the technician’s fee, and vary with brand, model and part source.
Frequently asked questions
Can I run the AC with this code?
Some models keep running, but without accurate temperature control.
Is this an expensive fault?
Usually not; it is one of the simpler repairs.
This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.
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