E37 Boiler Fault Code: What It Means on Every Brand

The E37 fault code appears on 2 brands — Alpha and Keston — and it does not mean the same thing on each. The same two or three characters can signal a pressure problem on one boiler and an ignition fault on another, so identify your brand first and use the table below to jump to the right page.

Up to: Lockout — engineer likely 2 brands use this code Meaning differs by brand

Which brand is your boiler?

The brand is printed on the front casing. Tap your brand for the full causes, fixes and repair costs.

Brand	What E37 means	Severity	DIY?
AAlpha	The E37 fault code on Alpha boilers indicates that the boiler has detected an abnormal operating condition and locked itself out as a safety measure. Full guide →	Lockout — engineer likely	No
KKeston	The E37 code appears on Keston boilers when the control system detects that the central heating water pressure has dropped to an unacceptably low level. Full guide →	Engineer may be needed	Some checks

E37 brand by brand

Alpha E37

The E37 fault code on Alpha boilers indicates that the boiler has detected an abnormal operating condition and locked itself out as a safety measure. Depending on your specific Alpha model — such as the Intec, E-Tec, Evoke, or Protec Plus — E37 can point to one of three underlying issues: low mains supply voltage reaching the boiler, a failure in the system pressure sensor (preventing the boiler from confirming safe operating pressure), or a malfunction with the flow temperature sensor. Because all three trigger the same lock-out behaviour, a Gas Safe registered engineer will need to diagnose which applies to your boiler if simple checks do not resolve it. Do not attempt to bypass the lock-out or force the boiler to fire — the shutdown exists to protect you and your home.

Causes, fixes & costs for Alpha E37 → · All Alpha codes

Keston E37

The E37 code appears on Keston boilers when the control system detects that the central heating water pressure has dropped to an unacceptably low level. The boiler monitors pressure continuously and will display E37 — typically alongside a flashing display — when pressure falls below roughly 0.5 bar, which is well beneath the safe operating range. The fault essentially tells you two things: check the system pressure, and consider whether the pressure sensor itself may be at fault. In most cases the fix is straightforward repressurisation via the filling loop, but if the boiler keeps losing pressure or the error persists after topping up, a Gas Safe registered engineer should investigate further. You can view the live pressure reading on a Keston boiler by pressing the 'Installer' button on the fascia repeatedly until '5' appears on the display — after a few seconds the screen shows the current pressure in bar.

Causes, fixes & costs for Keston E37 → · All Keston codes

Frequently asked questions

Is the E37 fault code the same on every boiler?

No. E37 means different things on different brands — see the table above. Always identify your boiler's brand (it is printed on the front casing) before acting on any advice about the code.

Can I fix a E37 fault myself?

On some brands there are safe homeowner checks first — typically system pressure, the condensate pipe in cold weather, and a single reset. Where the code is a simple pressure or reset condition, that may be all it needs. Never open the boiler casing yourself.

Who should I call about a E37 fault?

For gas boilers, a Gas Safe registered engineer — it is a legal requirement for any work on the appliance. If you smell gas at any point, leave the property and call the National Gas Emergency line on 0800 111 999.

General guidance only — not a substitute for professional advice, and not certified by a registered engineer. Any work on a gas appliance must be carried out by a Gas Safe registered engineer. If you smell gas, call 0800 111 999.