Your heat pump's internal computer chips are not communicating correctly because their configuration settings do not match each other.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Inverter not matched to Outdoor PCB dip switch setting
What causes this fault?
This fault occurs when the heat pump’s internal control boards are sending conflicting messages about how the system should operate. It usually happens because the physical switches on the main circuit board do not match the software settings on the inverter drive, preventing the unit from starting safely. This is typically caused by a component failure or a configuration error during a recent repair.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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 HF — 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.