LG heat pump errors: 33 CH codes and what to do

CH warnings on an LG Therma V air source heat pump identify a communication, water circulation, sensor, electronics or refrigerant circuit problem, but they do not confirm which component has failed. CH14 indicates insufficient water flow; CH05 means communication has been lost between units; and CH24 indicates high-pressure protection. The interpretation must be checked against the model: some meanings differ between split systems and R32 systems with a U3 outdoor unit. If the lockout returns, avoid repeated resets.

If you have a problem with your heat pump, you can use our free error code finder. It helps you identify errors and find straightforward, effective guidance on resolving them.

The model determines how the warning should be interpreted

The information collected here covers LG Therma V split references identified as AHUW, ZHBW and AHBW, and Therma V R32 systems with a 12 to 16 kW U3 outdoor unit. It is not a universal catalogue for every LG heat pump. The manual for the installed model takes priority where it specifies a different detection condition or includes warnings not listed in this table.

Identification is particularly important for CH22 and CH61. The former can refer to the current drawn by the entire outdoor unit or by the compressor, depending on the range. The latter distinguishes excessive condensing pressure in U3 units from a high temperature at an intermediate condenser pipe in split systems. The same brand and a similar appearance do not guarantee the same technical meaning.

Before resetting, photograph the display and find the indoor and outdoor unit references on accessible labels, without removing covers. It also helps to know whether the fault appeared during domestic hot water production, space heating or after a power cut. These details connect the warning to the operating conditions, rather than treating the number in isolation.

The 33 CH warnings covered for these Therma V ranges

The table separates the detected condition from its possible causes. A sensor reported as open or short-circuited may have a fault in the sensor itself, its connection or the circuit reading its signal. Similarly, a compressor protection warning describes why it has stopped, not necessarily the underlying problem. Internal checks are for an authorised technician.

Where the reference material limits a warning to a particular range, this is stated explicitly. Where descriptions are incomplete or conflicting, that uncertainty is retained: it is not safe to transfer a location, component or procedure from one version to another.

This is a collection of 33 reference codes, not 33 definitive diagnoses. It also does not establish which faults are most common: the available material provides no incident statistics. If a different number appears, or the machine manual gives a different description, do not substitute the closest-looking warning.

CH14 and CH10: water is not circulating as the system needs

CH14 means the pump is running but the system detects less water circulation than it needs. Possible hydraulic issues include restricted flow, contamination in filtration components, air or inadequate pump operation. The code identifies a water flow problem; it cannot distinguish between those causes without an installation assessment.

Pressure and flow are not the same thing. A pressure gauge can show pressure while very little water circulates, just as a road can be full of vehicles without traffic moving. If the controller displays pressure or flow readings, record them for comparison with the manual. There is no universal setting for every Therma V system here, and topping up water by guesswork is not safe.

On the split range covered here, CH10 points more specifically to a blocked BLDC pump. Users should not free its shaft, loosen plugs or open the pump body. Hydraulic filters must not be dismantled either: they may contain hot, pressurised water. Reading the display is accessible; opening the hydraulic circuit requires professional intervention.

Communication and sensor warnings do not condemn the board

CH03 places the problem between the wired controller and indoor unit. CH05 and CH53 concern communication between units, while CH52 relates to the main and inverter boards in the outdoor unit. Although all describe equipment failing to exchange information, these warnings are not interchangeable. A photograph prevents confusion between similar numbers and an inspection being directed at the wrong location.

CH57 needs extra care. Two reference descriptions place it between the outdoor main board and inverter board; another mentions transmission from the indoor unit to the outdoor inverter. That discrepancy cannot be resolved by choosing the most repeated explanation. What is clear is its connection to inverter communication in R32 U3 systems; the exact path must be checked in that unit’s documentation.

For sensor warnings, an open-circuit reading means the measurement circuit appears interrupted; a short circuit indicates an electrical condition inconsistent with the expected reading. This is not a reason to buy a sensor immediately. If the connection or electronic input is responsible, replacing the sensor will not fix the problem. Before buying parts, a technician needs to locate the signal fault through professional testing.

The quantity being measured matters too. CH41 concerns compressor discharge temperature, not the temperature of water sent to underfloor heating. CH08 relates to the domestic hot water cylinder, while CH44 refers to outdoor air. Confusing these locations can lead to an incompatible replacement part, even if the component is sold under a generic LG sensor description.

Pressure and compressor warnings: when to stop trying to restart

CH24, CH34 and CH35 describe pressure conditions in the refrigerant circuit. CH43 instead reports a high-pressure sensor signal fault. The distinction is essential: detecting abnormal pressure is different from being unable to measure it correctly. None of these warnings justifies adding refrigerant without diagnosis, and low pressure does not automatically confirm a leak.

CH21, CH22, CH23, CH26, CH27, CH29 and CH73 relate to protection, internal power supply, current consumption or compressor control. Diagnosis may require examining both the electronics and operating conditions. CH26 does not prove the compressor is beyond repair; CH21 alone does not prove the inverter board needs replacing. Diagnosis must separate the protection event from its cause.

When a pressure, temperature or current protection warning returns, repeated starts provide no useful user-level check. Do not touch pipes to judge their temperature, connect instruments or look for service valves. Refrigerant work requires an appropriately qualified professional; electrical testing and repairs require qualified personnel. That boundary still applies when the unit appears to be switched off.

What you can observe without opening the outdoor unit

External observation can provide useful information. From a safe position, look for bags, accumulated leaves or objects leaning against the unit that could obstruct airflow. Only remove loose, external obstacles, without putting hands through grilles or approaching the fan. Keeping airflow unobstructed is different from removing a guard to clean inside.

If CH67 appears and the fan is not turning, do not try to move it by hand or with a tool. There may be a blockage, a motor problem or a control fault, and the equipment may attempt to start. Breaking ice off the blades or applying hot water is not safe either. Visible ice is information for the diagnosis, not permission to work on moving components.

CH62 and CH65 illustrate another important distinction. The former describes excessive electronics temperature; the latter means a temperature measurement is invalid. Clearing the surrounding area does not prove the problem is resolved, and cleaning the casing does not repair a sensor. If the warning persists, internal cooling and temperature measurement need checking without the user removing panels.

A reset is not a repair

An earlier power cut can provide context for a communication fault, but it does not prove the fault is temporary. If the manual allows a reset from the controller, follow its instructions after recording the code. There is no universal disconnection time for every range. When the same warning returns, avoid repeated resets: the triggering condition remains present or requires diagnosis.

Recording what happened before resetting prevents useful information being lost. Alongside the photograph, note the active operating mode and whether the fault appeared at startup or after running for a while. If the controller offers a history view without entering service menus, that can also be photographed. Do not clear records or change technical settings to make the warning disappear, because hiding the message does not correct the fault.

In winter, completely disconnecting a heat pump is not always a neutral decision. Depending on the installation and model, it can disable frost protection functions. With low temperatures and water exposed outdoors, agree a safe shutdown arrangement with a technician. Stopping from the controller is not the same as cutting all power; equally, a unit with a burning smell or visible damage must not be kept running.

A diagnosis helps avoid replacing parts on guesswork

The number on the display cannot tell you the repair cost. A communication warning might lead to connection checks or an electronic fault diagnosis; a sensor warning might involve the sensor or its circuit. The available references provide no verifiable prices. Before accepting a repair, distinguish diagnosis, call-out, labour and parts, and check whether the visit is charged separately or credited against the repair: neither should be assumed.

The choice between repair and replacement does not depend on age alone. The system’s overall condition, the confirmed failed component, replacement part availability and the actual scope of work all matter. For a heat pump, comparison with a new system should include compatibility with the existing installation, not just the price of an outdoor unit. A useful quotation explains what has been checked and why that solution is proposed.

The code, model and circumstances provide a more reliable starting point than a series of improvised tests. Users can observe, document and perform actions expressly allowed by their manual; opening electronics, working on pressurised water or handling refrigerant falls outside that scope. With a locked-out Therma V, protecting safety and diagnostic information matters more than making CH disappear from the screen for a few minutes.