High
LED 6 (B) on Ferroli Hawk II

Your boiler has stopped working because it has detected an issue with its internal temperature sensors or water pressure levels, preventing it from safely heating your home.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

C.H. sensor (34) short circuit or resistance lower than 500 ohm; C.H. limit thermostat (50) open circuit (pump will run); C.H. water pressure low (114 open circuit)

From this model's manual
Verified against the Ferroli Boiler Hawk Ii installation & service manual.
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 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 →
Boiler cover options

Avoid the next call-out bill

A cover plan would handle faults like LED 6 (B): 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 guides you might find useful

Boiler keeps losing pressure

Six most common causes of dropping pressure.

Read →

Boiler won't turn on — 9-step checklist

Work through these before the call-out.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →