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Error code reference

LG Hvac Error Code E652

Communication error by installing COM1 dual MASTER

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Communication error by installing COM1 dual MASTER — more than two MASTERs are set.

First step from the service manual

Check K8 of SW05 option setup switch on PCB to verify MASTER/SLAVE is set properly.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What E652 means on a LG hvac

Error code E652 on LG HVAC systems indicates a communication conflict caused by having more than two units configured as MASTER within a COM1 dual MASTER setup. In a properly configured multi-unit system, the COM1 network relies on a strict MASTER/SLAVE hierarchy to coordinate communication between units. When two or more units are both designated as MASTER on the same communication bus, the network cannot arbitrate control signals correctly, resulting in a communication failure and the E652 fault being triggered.

The MASTER/SLAVE designation is controlled physically through the option setup switch SW05 on the PCB, specifically the K8 position. Each unit in the system must have this switch set according to its intended role in the network. If multiple units were installed or replaced without careful attention to the SW05 switch configuration, it is possible for more than one unit to be left in the MASTER position, creating the conflict that generates this error.

Diagnosing E652 requires physically inspecting the SW05 switch on the PCB of each unit connected to the COM1 bus and confirming that only the designated MASTER unit has K8 set to the MASTER position. All remaining units must be set to SLAVE. Failing to resolve the duplicate MASTER configuration will prevent normal communication from being restored, regardless of power cycling or other reset attempts.

Source: manufacturer service documentation.

Common causes of E652

  1. 01

    Multiple units set to MASTER via SW05 K8 switch

    Wiring / connection

    The most direct cause is having the K8 position on the SW05 option setup switch configured to MASTER on more than one unit in the COM1 network. Each unit's PCB must be inspected and only one should remain in the MASTER position.

  2. 02

    Incorrect switch configuration during installation

    Wiring / connection

    During initial installation or system expansion, technicians may not have adjusted the SW05 K8 switch on newly added units, leaving factory or default settings that conflict with the existing MASTER unit.

  3. 03

    PCB replacement without reconfiguring the switch

    Wiring / connection

    If a PCB was replaced on any unit in the system, the SW05 K8 switch on the new board may default to MASTER, creating a duplicate MASTER condition on the network.

  4. 04

    Faulty SW05 switch holding incorrect position

    Part replacement

    A damaged or worn SW05 switch may not hold its set position reliably, causing a unit to revert to MASTER even after being correctly configured. If the switch is physically defective, board-level repair or PCB replacement may be necessary.

  5. 05

    Wiring or bus connection error causing signal crossover

    Wiring / connection

    Incorrect COM1 bus wiring between units can cause communication signals to be misread, potentially making a SLAVE unit appear as a second MASTER to the network. Inspect all COM1 wiring connections for proper routing and secure termination.

See the test procedure for each cause

Frequently asked questions about E652

What does E652 mean on a LG hvac?
E652 indicates a communication error caused by more than one unit being configured as MASTER on the COM1 dual MASTER network. LG HVAC multi-unit systems require a strict hierarchy where only one unit acts as MASTER and all others are set to SLAVE. When this configuration is violated, the system cannot communicate properly and displays E652. The fix involves checking the K8 position on the SW05 option setup switch on the PCB of each connected unit.
How do I fix the E652 error on my LG HVAC system?
Fixing E652 requires accessing the PCB on each unit connected to the COM1 bus and inspecting the SW05 option setup switch, specifically the K8 position. Only one unit in the system should have K8 set to MASTER, and all other units must be set to SLAVE. Once the duplicate MASTER designation is corrected, the communication conflict should be resolved. This process typically requires a qualified HVAC technician since it involves working with internal electrical components.
Is the E652 error on a LG HVAC system a safety concern?
E652 is primarily a communication configuration error rather than a safety hazard involving high-voltage or refrigerant risks. However, because the error disrupts system communication, the HVAC equipment may not operate correctly or at all while the fault is active. You should avoid running the system in a faulted state for extended periods and have a technician correct the switch configuration promptly to prevent further operational issues.
Will resetting the LG HVAC unit clear the E652 error?
A simple power reset will not permanently clear the E652 error because the underlying cause, a duplicate MASTER switch configuration, remains in place after power is restored. The system will detect the conflicting MASTER designations on the COM1 bus again and re-trigger the fault. The SW05 K8 switch on the affected unit or units must be physically corrected before the error will be resolved.
How much does it cost to repair an E652 error on a LG HVAC system?
If the fix only requires reconfiguring the SW05 K8 switch on the PCB, the cost is primarily a service call and labor fee, which typically ranges from $75 to $200 depending on your location and technician rates. If the SW05 switch itself is damaged and a PCB replacement is needed, total costs including parts and labor could range from $300 to $800 or more. Getting a diagnostic quote from a certified LG HVAC technician before authorizing any parts replacement is advisable.

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