13 Boiler Fault Code: What It Means on Every Brand

The 13 fault code appears on 2 boiler brands — Intergas and Johnson & Starley — and on all of them it points to the same kind of problem. The details still differ by brand (thresholds, sub-codes, reset procedure), so use the table below to jump to the page for your boiler.

Lockout — engineer likely 2 brands use this code

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 13 means	Severity	DIY?
IIntergas	Fault code 13 on an Intergas boiler indicates a problem with the S1 sensor on the heat exchanger. Full guide →	Lockout — engineer likely	No
JSJohnson & Starley	Fault code 13 (shown as E13 on the display) is a safety lockout that appears across several Johnson & Starley ranges — including the Quantec, Reno, WarmCair, and Economaire. Full guide →	Lockout — engineer likely	No

13 brand by brand

Intergas 13

Fault code 13 on an Intergas boiler indicates a problem with the S1 sensor on the heat exchanger. Intergas boilers use two sensors on the heat exchanger — S1 monitors the flow side and S2 monitors the return — and fault codes 10 to 14 all relate to this sensor group. Code 13 specifically flags an issue with the S1 reading, meaning the boiler cannot confirm the heat exchanger is operating safely. As a result, the boiler will typically lock out and refuse to fire until the underlying problem is diagnosed and resolved, after which a reset is required to clear the code.

Causes, fixes & costs for Intergas 13 → · All Intergas codes

Johnson & Starley 13

Fault code 13 (shown as E13 on the display) is a safety lockout that appears across several Johnson & Starley ranges — including the Quantec, Reno, WarmCair, and Economaire. Depending on your specific model, it signals one of two related problems: either the boiler's flue gases have exceeded a safe temperature threshold and the appliance has shut itself down to prevent damage, or the control system has detected a flame sensing or gas pressure failure during operation. In both cases the boiler locks out until the underlying fault is identified and resolved. Because fault code numbering is not consistent across all Johnson & Starley product ranges, you should cross-reference with your own model's manual or contact Johnson & Starley directly on 01604 762881 to confirm the exact meaning for your appliance.

Causes, fixes & costs for Johnson & Starley 13 → · All Johnson & Starley codes

Frequently asked questions

Is the 13 fault code the same on every boiler?

Broadly, yes — on Intergas and Johnson & Starley the 13 code points to the same class of fault, and the recommended response is similar. Model-specific details such as sub-codes and reset procedures still vary, so follow the page for your own brand.

Can I fix a 13 fault myself?

Not usually. On every brand listed, 13 points to a fault that needs a suitably registered engineer to diagnose and repair. A single reset to rule out a transient glitch is reasonable; repeated resets are not.

Who should I call about a 13 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.