S.53 Medium
Your boiler is pausing temporarily because it is struggling to circulate water quickly enough to keep the system cool.
Technical description: Boiler is in waiting period of modulation f block function due to water shortage
Typical repair cost: £100-350 (including labour)
DIY fix possible
Check that the boiler pressure is between 1.0 and 1.5 bar on the displayEnsure all radiator valves (TRVs) are fully open to allow water flowCheck that the blue isolation valves underneath the boiler are in the 'open' position
Protect yourself from future repair bills
A boiler cover plan would cover faults like S.53 — 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
- Central heating pump
- Main heat exchanger (flushing/cleaning)
- Pressure sensor
*Affiliate links — we may earn a commission at no extra cost to you.