High
S.13 on Vaillant ecoTEC exclusive System

Your boiler is struggling to light its flame, which means you may experience intermittent issues with your heating and hot water.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

What the manual says

Manufacturer manual

DHW mode: Ignition

From this model's manual
Verified against the Vaillant Ecotec Exclusive Combi installation & service manual, page 41.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

What causes this fault?

This fault occurs when the boiler's control system attempts to start the heating process but fails to detect a stable flame through the ignition electrodes. The most common reasons are a worn-out spark probe that can no longer create a spark or a faulty gas valve that isn't delivering enough fuel to the burner.

This fault is more frequent during the first cold snap of autumn when a boiler is suddenly worked harder after sitting idle all summer.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

Find a Gas Safe engineer
Search the official register →

Avoid the next call-out bill

A cover plan would handle faults like S.13: no call-out fees, no surprise bills.

Approved partner
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Get a quote →

Affiliate links. We may earn a commission at no extra cost to you.

Related fault codes

Related guides you might find useful