CH16 on a LG heat pump: Problems in sensors – water-inlet, water-outlet and backup-heater outlet sensors (CH17/18/19) fail at the same time
Short answer
On a LG heat pump, CH16 means: Problems in sensors – water-inlet, water-outlet and backup-heater outlet sensors (CH17/18/19) fail at the same time. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Problems in sensors – water-inlet, water-outlet and backup-heater outlet sensors (CH17/18/19) fail at the same time.
Part involved: water inlet/outlet/heater-outlet thermistors.
When it shows: More than one of the water sensors shows invalid data simultaneously (High Temperature split: water inlet and outlet sensors open/short simultaneously).
Likely causes:
- Heater-out / water temperature sensors improperly connected or mixed up; multiple sensor damage; sensor not inserted in pipe.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: no.
Manual reset: Service-engineer repair and restart required (LG: resumed only after certificated professional's check).
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. This is an 'Error'-class fault: LG says the system can only be resumed after a qualified professional has checked it, so do not keep trying to restart it.
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. Check the sensor housings are on the correct connectors (housing colours) and fixed with sensor holders.
Who to ask for: Heat pump engineer (controls, sensors, PCB).
Certification: None statutory beyond electrical competence (BS 7671).
What you might notice
Sources
- AIR-TO-WATER HEAT PUMP SERVICE MANUAL (General) – R32 Hydrosplit, MFL68682007 ↗ · MFL68682007 · page 71, 92-93 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026