BoilerFaultCodesYour boiler has lost connection with its outdoor thermometer, meaning it cannot automatically adjust your heating based on the weather outside.
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.
Technical description: Outdoor sensor not detected.
What causes this fault?
This fault occurs when the boiler's control board loses the electrical signal from the external weather sensor mounted on your outside wall. The most common reasons are a break in the thin communication wire, loose connections at either end, or the sensor hardware failing due to moisture ingress. When this happens, the boiler can no longer calculate the most efficient temperature for your radiators based on the outdoor climate.
This fault is frequently discovered during the first cold snap of autumn when the sensor is required to ramp up the heating demand after being idle all summer.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like CC — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Worcester Bosch Greenstar 30HE is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
Affiliate links — we may earn a commission at no extra cost to you.