CH49 on a LG THERMA V High Temperature Split: Defective IPM temperature sensor – outdoor unit (R410A stage) error on High Temperature split; shown on outdoor 7-segment LED with unit number suffix (e.g. "49 1") and on the indoor display/remote controller
Short answer
On a LG heat pump, CH49 means: Defective IPM temperature sensor – outdoor unit (R410A stage) error on High Temperature split; shown on outdoor 7-segment LED with unit number suffix (e.g. "49 1") and on the indoor display/remote controller. The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Defective IPM temperature sensor – outdoor unit (R410A stage) error on High Temperature split; shown on outdoor 7-segment LED with unit number suffix (e.g. "49 1") and on the indoor display/remote controller.
Part involved: outdoor unit (R410A stage).
When it shows: Disconnection or short circuit on IPM temperature sensor of the outdoor unit.
Likely causes:
- Disconnection or short circuit on IPM temperature sensor of the outdoor unit.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: yes – trouble clears when the condition is repaired; emergency operation must be restarted by the user after a power reset.
Manual reset: Not normally required; user restarts after power reset if emergency operation was running.
What you can check
- Read the code on the controller (LG shows 'CH' + number; older wired controllers alternate 'CH' and the number) and note it together with the model number. Report it to your installer or an LG-authorised service centre – LG owner's manuals say an error code generated by self-diagnosis is a reason to call the service. For this 'trouble' class LG allows temporary emergency operation: if the controller shows a pop-up offering it you may accept (OK) as a stop-gap; running costs will be higher, so do not use it long term. Emergency operation does not restart by itself after a power cut – you must switch it back on at the controller. Check (without opening any panels) that the outdoor unit is not blocked by leaves, debris, snow or ice and that nothing is stacked against the coil or fan grille.
What the engineer will check
- Check the thermistor is fully inserted in its pocket/holder and the connector is seated on the correct PCB header; measure resistance unplugged (LG: pipe/water sensors 5 kΩ at 25 °C, room air sensor 10 kΩ at 25 °C, D-pipe sensor ~200 kΩ at 25 °C) and voltage plugged (~2.2–2.5 V DC at 25 °C) against LG resistance-temperature tables; replace sensor, then PCB if readings are correct.
Who to ask for: Heat pump engineer (controls, sensors, PCB).
Certification: None statutory beyond electrical competence (BS 7671).
What you might notice
Sources
- LG THERMA V High Temperature Installation Manual (AHUW166T3 / AHNW166T3 cascade R410A/R134a), MFL67212828 Rev.00 (2019) – ManualsLib 1770589 ↗ · MFL67212828 Rev.00_051519 · page 121-122 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026