Problem in water tank sensor
The CH08 error code on Lg boilers indicates problem in water tank sensor.
Lg CH08 means: problem in water tank sensor. On this component the documented failure modes are the tank sensor has failed — short circuit or open circuit or wiring, connector or harness of the tank sensor damaged or loose. You can safely reset the boiler once — if CH08 returns, do not keep resetting. A qualified heating engineer should diagnose the root cause.
What Does CH08 Mean
The CH08 code is shown by the boiler’s control board when it detects problem in water tank sensor. The boiler then stops instead of continuing to run in that condition: the code is the appliance reporting a problem, not proof that the boiler is broken.
| What you see on the boiler |
|---|
| The display shows CH08 and the boiler stops until the fault is cleared |
Common Causes
The manufacturer does not publish a cause list for this specific code. The causes below are the failure modes documented for the same component on other boilers, confirmed by the service literature of 8 different manufacturers.
| Cause |
|---|
| The tank sensor has failed — short circuit or open circuit |
| Wiring, connector or harness of the tank sensor damaged or loose |
Safety Warning
CH08 involves electrical or pressure-related components. Do not attempt repairs without proper qualifications. Ensure the boiler is electrically isolated before any inspection. If you notice water leaks, unusual sounds, or pressure anomalies, contact a qualified heating engineer immediately.
Parts & Prices
Prices shown are indicative. Actual prices and availability vary by region.
Step-by-Step Diagnosis
Note the exact error code and check the manufacturer's installation and service manual for specific guidance
Check all visible wiring connections for security and condition
Power cycle the boiler — switch off at the mains for 30 seconds, then switch back on
If the fault recurs, check the fault history for related or recurring codes
Inspect the boiler for any obvious signs of damage, leaks, or unusual sounds
How to Fix It
Reset the boiler after investigation
repair any loose connections or damaged wiring
replace the faulty component identified during diagnosis
if the fault persists after basic checks, contact a qualified heating engineer with the exact error code
Measure the resistance of the tank sensor with a multimeter and compare it against the manufacturer’s resistance-versus-temperature table; replace it if it is open circuit, short circuit or out of range.
Unplug and re-seat the connector of the tank sensor, then check the harness for chafing, corroded pins and breaks in continuity.
Refer to the Lg service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
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Affected Models
Lg models that can display fault code CH08:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Lg models | — | Possible |
Frequently Asked Questions
Reset the boiler after investigation. According to the technical documentation, this is the first check on the list for CH08.
CH08 is not classified as a high-severity fault, so the boiler can be reset once. If CH08 comes back, stop resetting: the underlying cause is still there and needs a qualified heating engineer.