433 High
Your boiler has shut down because it has detected that it is getting far too hot, likely due to water not circulating properly through the system.
Technical description: Heat exchanger temperature exceeded (greater than 95 degrees)
Typical repair cost: £120-£350 (including labour)
DIY fix possible
Check that your radiator valves are fully openEnsure there is enough water pressure in the system (usually between 1 and 1.5 bar)Bleed your radiators to remove any trapped airReset the boiler using the selector switch
Protect yourself from future repair bills
A boiler cover plan would cover faults like 433 — no call-out fees, no surprises.
*Affiliate links — we may earn a commission at no extra cost to you. Prices shown are starting prices.
Parts commonly replaced
- Pump
- Main Heat Exchanger
- Temperature Sensor (NTC)
- Diverter Valve
*Affiliate links — we may earn a commission at no extra cost to you.