Low
t6 on Worcester Bosch 24/28/35 CDi MkII

Your boiler is performing a self-check of its internal sensors, and this code indicates that a safety test is currently active to ensure the flame detection system is working correctly.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

What the manual says

Manufacturer manual

Ionisation oscillator test. Ionisation circuit is switched on. An A.C. voltage of approximately 150 Volts can be measured between the ionisation probe and earth.

From this model's manual
Verified against the Worcester Bosch Greenstar Cdi Compact installation & service manual, page 71.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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