CH03 on a LG heat pump: Bad communication between wired remote controller and indoor unit (Main PCB(Indoor) does not receive the remote controller signal)
Short answer
On a LG heat pump, CH03 means: Bad communication between wired remote controller and indoor unit (Main PCB(Indoor) does not receive the remote controller signal). 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: Bad communication between wired remote controller and indoor unit (Main PCB(Indoor) does not receive the remote controller signal).
Part involved: wired remote controller / CN_REMO cable.
When it shows: No communication between Main PCB(Indoor) and wired remote controller for a set time; PCB CN_REMO should supply 12 V DC.
Likely causes:
- Incorrect cable connection or burnout; noise interference; wired remote controller failure; indoor Main PCB failure; wrong RMC software.
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. Check the controller has power (display lit) – nothing else is user-serviceable.
What the engineer will check
- Check remote-controller connector and terminal block, cable specification (AWG24 3-core or better), no intermediate twisted joints, no short/open (continuity check with connectors removed), 12 V DC at CN_REMO; replace remote controller or indoor Main PCB. After replacing controller or PCB re-enter installer settings.
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, 76, 80-81 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026