- Heat pumps
- Air-to-water heat pump
CH03
LG CH03 on Therma V heat pump: remote controller link fault
Risk level
Low
Usually safe to check without specialist tools.
Urgency
Medium
Quick answer
Code CH03 or 03 means poor communication between the wired remote controller and the main PCB on your LG Therma V heat pump, so inspect the screen and try a single reboot. If the fault returns after rebooting, write down the code and book an authorised LG technician without opening any cover.
Safety first
Stop and check this first
- Do not remove the heat pump cover or touch internal circuit boards yourself: LG manuals require isolating mains power and waiting at least 10 minutes for internal capacitors to discharge before a qualified technician accesses electrical parts.
- Never connect or splice the remote controller cable while power is switched on, as live wiring work can damage the control PCB and trigger communication failures.
Safe checks you can perform
- Record the exact 03 or CH03 display state on the RS3 wired controller
- Inspect the wall-mounted controller externally for warping or cable strain
- Perform a single system reboot from the wired controller menu
Leave these tasks to a qualified professional
- Do not attempt this professional task: Inspect CN_REMO terminal seating, cable continuity, and 50 m length limit
- Do not attempt this professional task: Measure 12 V DC output at the Main PCB (Heater) before replacing parts
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Inspect CN_REMO terminal seating, cable continuity, and 50 m length limit
What they doAn authorised technician or installer must check that the 3-wire harness between the remote controller and Main PCB assembly (Heater) is firmly seated, verify continuity on the Red, Yellow, and Black/Brown cores, and confirm total cable length does not exceed 50 m or suffer wall-plate distortion.
They must show youthe physical condition of the CN_REMO connector, continuity across all three conductors, and flat seating of the controller installation plate.
In writingthe verified cable run condition, connector inspection result, and confirmation that the mounting plate sits flush without twisting the housing.
Measure 12 V DC output at the Main PCB (Heater) before replacing parts
What they doIf the harness and connectors pass inspection, the technician must measure the DC supply output on the Main PCB assembly (Heater) against LG's 12 V DC normal condition specification before condemning either the PCB or the remote controller.
They must show youthe multimeter reading showing whether the PCB outputs 12 V DC to the remote controller port and live communication recovery.
In writingthe measured DC voltage at the PCB header, part reference of any replaced component, and the official LG service job or case number.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Record the exact 03 or CH03 display state on the RS3 wired controller
- Who:
- you.
- How:
- check the wired remote screen on your LG Therma V and note whether it displays CH03 or code 03 alongside the fault icon, and whether button presses still register on screen.
- Result that matters:
- having the exact error code and screen responsiveness recorded for LG customer support.
- If the keypad still responds:
- proceed to check external wall mounting and run a single system reboot.
- If the screen is blank or frozen:
- note the symptom without prizing open the controller casing.
- Evidence to keep:
- clear photo of the wired remote controller screen showing error 03 or CH03.
Evidence: LG air to water heat pump owner's manual MFL68026705
Inspect the wall-mounted controller externally for warping or cable strain
- Who:
- you.
- How:
- without unscrewing the unit or opening any cover, look at the controller frame against the wall to see if an uneven surface is twisting the casing or pinching any visible cable section.
- Result that matters:
- confirming whether external mounting distortion or visible cable damage is present.
- If the controller frame looks bowed against the wall:
- mention this so the technician can level the backplate.
- If the casing sits flat with no visible cable damage:
- move on to a single reboot from the menu.
- Evidence to keep:
- side-angle photo of the controller mounted on the wall and any exposed cable entry.
Evidence: LG Therma V R32 Monobloc air to water heat pump installation manual MFL68026607
Perform a single system reboot from the wired controller menu
- Who:
- you.
- How:
- if the buttons respond, open User Setting and select System Reboot, or press and hold the [On/Off + Back] buttons together for 5 seconds once to force a controller restart.
- Result that matters:
- testing whether communication between the wired controller and main PCB recovers cleanly.
- If CH03 clears and normal operation resumes:
- monitor the controller to ensure the fault does not return.
- If CH03 or 03 reappears after one reboot:
- do not repeat the reset and book an authorised LG technician.
- Evidence to keep:
- note of the reboot time and photo of the controller display after restarting.
Evidence: LG air to water heat pump owner's manual MFL68026705
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Heat pumps
- Brand
- LG
- Product type
- Air-to-water heat pump
Known code variants
- 03
- CH 03
- CH03 HM091MR
- CH03 LG Therma V
- error CH03 aerotermia LG
- fallo 03 bomba de calor LG
- LG air to water code 03
- LG heat pump error CH03
- LG Therma V CH03
- remote controller communication fault LG
- sin comunicacion mando Therma V
What it means
In the LG Therma V R32 Monobloc installation manual MFL68026607 and owner's manual MFL68026705 for HM, HN, and HU air-to-water heat pumps with the RS3 wired controller, error 03 (CH03) means bad communication between the remote controller and the unit. Other LG series or controller revisions may differ. LG's diagnostic table specifies that the wire connection to the Main PCB assembly (Heater) must be tight and PCB output must read 12 V DC at CN_REMO; the code alone never proves the controller or PCB has failed, as a loose plug, a cable run over 50 m, or a warped wall plate causes the same symptom.
Warnings and stop conditions
- Higheditorial warning
Do not remove the heat pump cover or touch internal circuit boards yourself: LG manuals require isolating mains power and waiting at least 10 minutes for internal capacitors to discharge before a qualified technician accesses electrical parts.
Evidence: LG Therma V R32 Monobloc air to water heat pump installation manual MFL68026607 · LG air to water heat pump owner's manual MFL68026705
- Mediumeditorial warning
Never connect or splice the remote controller cable while power is switched on, as live wiring work can damage the control PCB and trigger communication failures.
Evidence: LG Therma V R32 Monobloc air to water heat pump installation manual MFL68026607
Symptoms and causes
Probable causes · in order
- Loose CN_REMO plug or damaged 3-core cable between controller and PCBCommon
The three-conductor communication cable (Red 12 V DC, Yellow Signal, Black or Brown GND) is not seated tightly in the CN_REMO header on the main PCB or has a damaged core along the wall run.
Evidence: LG Therma V R32 Monobloc air to water heat pump installation manual MFL68026607
- Remote controller extension cable total length exceeding 50 metresPossible
Manual MFL68026607 states that the factory cable is 10 m and warns against extending the total wiring past 50 m with PZCWRC1 (AWG 24) extension leads because communication errors will occur.
Evidence: LG Therma V R32 Monobloc air to water heat pump installation manual MFL68026607
- Twisted wall installation plate or overtightened mounting screwsPossible
Fastening the controller backplate onto an uneven wall surface or overtightening the fixing screws twists the remote housing and prevents reliable internal connector contact.
Evidence: LG Therma V R32 Monobloc air to water heat pump installation manual MFL68026607
- Missing 12 V DC output from the Heater PCB or faulty remote controllerLess common
The Main PCB assembly (Heater) stops supplying the required 12 V DC (rated 11 to 12 V DC, 5 mA) to the remote bus, or the transceiver inside the wired controller is defective.
Evidence: LG Therma V R32 Monobloc air to water heat pump installation manual MFL68026607
Virtual technician
Does CH03 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
LG Therma V R32 Monobloc air to water heat pump installation manual MFL68026607
LG Electronics · 2026 · manual
- 2
LG air to water heat pump owner's manual MFL68026705
LG Electronics · 2026 · manual
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