BoilerFaultCodesYour heat pump’s internal power electronics have become too hot and have shut the system down to prevent damage.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Inverter High Temperature
What causes this fault?
This fault occurs when the power electronics that drive the heat pump compressor reach a safety temperature limit. It is usually caused by a failure of the internal cooling fan or a build-up of dust and debris blocking the heatsink, preventing the system from shedding heat effectively. When the electronics cannot stay cool, the unit shuts down to prevent permanent component failure.
This fault is more common during summer heatwaves, as high ambient temperatures make it harder for the unit's internal cooling system to keep the electronics within safe limits.
DIY fix possible
Check that the outdoor unit is not covered or its air vents blocked by leaves or debris.Ensure there is at least a one-metre clear space around the outdoor unit for proper airflow.Turn the power to the unit off at the isolator switch, wait 5 minutes, and turn it back on to see if the code clears once cooled.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like LC9 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
Affiliate links — we may earn a commission at no extra cost to you.