- Heat pumps
- Air-to-water heat pump
CH17
LG Therma V CH17 heat pump error: water inlet sensor fault
Risk level
Low
Usually safe to check without specialist tools.
Urgency
Medium
Quick answer
CH17 on an LG Therma V points to a problem with the temperature sensor on the water entering the unit. You can accept emergency mode if the controller offers it and call service so they can measure the sensor and its connection.
Safety first
Stop and check this first
- LG states that customers must not install, remove, inspect or repair the unit themselves because of the risk of fire, electric shock or explosion. Measuring sensors and touching the board is a job for service staff.
- The LG owner's manual advises against switching off the power even when the unit is unused for a long time, because protections such as pump anti-locking do not run without power.
Safe checks you can perform
- Accept emergency mode if offered
- Restart after a power cut
- Keep an eye on domestic hot water
Leave these tasks to a qualified professional
- Do not attempt this professional task: Measure the water inlet probe
- Do not attempt this professional task: Inspect wiring and plug
- Do not attempt this professional task: Replace probe or board only on evidence
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.
Measure the water inlet probe
What they doThe technician unplugs the probe to measure its resistance, then plugs it back to measure the voltage at the board connector.
They must show youthe measured resistance and the water temperature at that moment, compared with LG's table.
In writingthe readings, the reference temperature and the conclusion.
Inspect wiring and plug
What they doBefore replacing parts, they check that the probe plug is fully seated and the cable to the board is undamaged.
They must show youthe plug before and after the inspection.
In writingwhat was wrong with the wiring and how it was fixed.
Replace probe or board only on evidence
What they doIf the probe measures fine and no voltage arrives, the board is assessed; if the probe is out of range, the probe is replaced.
They must show youthe measurements that justify the chosen part.
In writingthe part replaced, its reference and the result of the final test.
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.
Accept emergency mode if offered
- Who:
- you, at the controller.
- How:
- many units show a pop-up when they detect slight sensor trouble. According to the owner's manual, the unit carries on in emergency mode once you press OK on that pop-up.
- Result that matters:
- keeping some heating until the technician arrives.
- If the pop-up appears:
- press OK and check that the house warms up.
- If there is no option and the unit stays stopped:
- call service.
- Evidence to keep:
- photo of the screen with the code and the pop-up.
Evidence: LG air to water heat pump owner's manual MFL68026705
Restart after a power cut
- Who:
- you.
- How:
- if power drops while the unit is in emergency mode, LG explains that it will not restart on its own, to protect itself. When power returns, switch it back on yourself from the controller.
- Result that matters:
- the house is not left cold after an outage.
- If the unit starts again:
- keep waiting for the service visit.
- If it does not start or shows another code:
- write it down and tell the technician.
- Evidence to keep:
- note with the time of the outage and of the restart.
Evidence: LG air to water heat pump owner's manual MFL68026705
Keep an eye on domestic hot water
- Who:
- you.
- How:
- check whether the hot water tank is still heating. LG warns that sanitary water heating may not be possible during emergency operation.
- Result that matters:
- knowing which services the unit keeps during the fault.
- If there is no hot water:
- tell the technician so they factor it in.
- If water is still heating:
- note that as well.
- Evidence to keep:
- note of the hot water temperature if the controller shows it.
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
- aerotermia LG CH17
- bomba de calor LG CH17
- CH17
- error 17 LG Therma V
- LG air to water CH17
- LG heat pump CH17
- LG monobloc CH17
- LG Therma V CH17
- LG Therma V error 17
- LG Therma V sensor entrada agua
- LG Therma V water inlet sensor
What it means
The error table in the LG Therma V R32 Monobloc installation manual (2026, English only) lists display number 17 as a problem in the water inlet sensor. LG gives three causes: a poor connection between sensor and board, a board fault or a sensor fault, and sets about 5 kΩ at 25 °C unplugged and 2.5 V DC plugged in as the reference. The owner's manual treats sensor faults as slight trouble that allows emergency operation. The code alone does not confirm which of the three parts is at fault.
Warnings and stop conditions
- Highsource verified
LG states that customers must not install, remove, inspect or repair the unit themselves because of the risk of fire, electric shock or explosion. Measuring sensors and touching the board is a job for service staff.
Evidence: LG Therma V R32 Monobloc air to water heat pump installation manual MFL68026607
- Mediumsource verified
The LG owner's manual advises against switching off the power even when the unit is unused for a long time, because protections such as pump anti-locking do not run without power.
Evidence: LG air to water heat pump owner's manual MFL68026705
Symptoms and causes
Probable causes · in order
- Loose link between sensor and boardCommon
A badly seated plug or a damaged wire between the probe and the unit's board gives impossible readings and raises the warning.
Evidence: LG Therma V R32 Monobloc air to water heat pump installation manual MFL68026607
- Damaged water inlet probePossible
If the probe's resistance drifts away from the 5 kΩ at 25 °C given by LG, the sensor reports a false temperature or none at all.
Evidence: LG Therma V R32 Monobloc air to water heat pump installation manual MFL68026607
- Electronic board faultLess common
LG also lists the board that reads the sensor; with a healthy probe, the 2.5 V DC would then be missing at the plug.
Evidence: LG Therma V R32 Monobloc air to water heat pump installation manual MFL68026607
Virtual technician
Does CH17 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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