LG Heat Pump Error Code CH08

CH08 indicates a problem in the water tank temperature sensor circuit. The main PCB is not receiving a valid signal from the NTC thermistor that monitors water tank temperature. The expected resistance is 5k ohms at 25 degrees Celsius when the sensor is unplugged, and the expected voltage at the connector is 2.5Vdc at 25 degrees Celsius when plugged in. Any significant deviation from these values points to a sensor, wiring, or connection fault.

A reset may temporarily clear the CH08 code, but the error will return if the underlying fault is not corrected. If the sensor is disconnected, failed, or wiring is damaged, the PCB will detect the problem again as soon as it checks the sensor circuit. A reset is useful for confirming whether a fault is intermittent, but it is not a substitute for proper diagnosis and repair.

Repair costs depend on the root cause. If the fix is simply reseating a connector, there may be no parts cost at all, with labor being the primary expense. A replacement NTC thermistor sensor typically costs in the range of 20 to 80 dollars for the part. If the main PCB requires replacement, costs can range from 200 to 600 dollars or more including parts and labor, depending on the model and service rates in your area.

Some causes of CH08 are accessible to a knowledgeable DIYer. Checking and reseating the sensor connector requires no special tools. Measuring sensor resistance with a multimeter is also straightforward if you are comfortable working near electrical components with the unit powered down. However, if the wiring harness or PCB needs replacement, a qualified technician is recommended to ensure safe and correct repair.

Operating the heat pump while CH08 is active is not recommended. The unit relies on accurate water tank temperature data to control heating safely and efficiently. Without a valid sensor reading, the system cannot regulate temperature correctly, which could lead to overheating or improper operation. Most units will restrict or shut down operation automatically when this fault is present.