Samsung · Split air conditioners · Samsung WindFree AR50F / AR60F / AR70F (wall-mounted split, R32)
C121Indoor unit room (return air) temperature sensor is open/short
Name in the manufacturer's documentation (service manual): Indoor unit room (return air) temperature sensor is open/short
[1]
In plain words (editorial)
The indoor room (return air) temperature sensor is open or short-circuited. The checks in the service manual (wiring, sensors, PCBs, refrigerant) are for a qualified air-conditioning technician.
When to call a service technician: Contact an authorised Samsung service technician.
✎ editorial – written from the cited sources, not a manufacturer statement. Status: draft.
For technicians
Steps given by the manufacturer (source text)
- Detach the sensor from the PBA connector (CN100) and measure the resistance with an ohmmeter; reconnect the sensor connector if needed.[2]
- If the resistance is wrong: replace the sensor assembly.[3]
- Connect the sensor, supply power and measure the voltage at CN100 #10-#12; below 0.5 V or over 4.5 V → exchange the indoor PBA.[4]
⚠ Work on refrigerant circuits, mains electricity and PV DC wiring is for qualified technicians only.
The Polish page has more detail (plain-language explanation, safe checks, guides): Read in Polish →
Sources
Every statement has a footnote to the document and PDF page. “Quote verified” means the quote was found automatically in the text of that page.
- [1] Samsung – Split-type Air Conditioner Service Manual (indoor AR50F/AR60F/AR70F…C1A…NEU, outdoor …XEU), „GEO WIND FREE EU RS9 25R” (RS9 25R (2025-10-01, wg nazwy pliku)) , p. 19 manufacturer document – copy from a distributor quote verified
Indoor unit room (return air) temperature sensor is
- [2] Samsung – Split-type Air Conditioner Service Manual (indoor AR50F/AR60F/AR70F…C1A…NEU, outdoor …XEU), „GEO WIND FREE EU RS9 25R” (RS9 25R (2025-10-01, wg nazwy pliku)) , p. 73 manufacturer document – copy from a distributor quote verified
Detach the assembled sensor from the PBA
- [3] Samsung – Split-type Air Conditioner Service Manual (indoor AR50F/AR60F/AR70F…C1A…NEU, outdoor …XEU), „GEO WIND FREE EU RS9 25R” (RS9 25R (2025-10-01, wg nazwy pliku)) , p. 73 manufacturer document – copy from a distributor quote verified
Assy Sensor Replace
- [4] Samsung – Split-type Air Conditioner Service Manual (indoor AR50F/AR60F/AR70F…C1A…NEU, outdoor …XEU), „GEO WIND FREE EU RS9 25R” (RS9 25R (2025-10-01, wg nazwy pliku)) , p. 73 manufacturer document – copy from a distributor quote verified
Below 0.5V or Over 4.5V?