BoilerFaultCodesWhat the manual says
Manufacturer manualDifferential fan pressure status
What causes this fault?
This fault occurs when the boiler's internal safety sensors detect that the fan isn't moving enough air to safely vent exhaust gases outside. The most common reasons are a build-up of dirt or debris in the small plastic tubes inside the unit, or the fan motor itself failing after years of heavy use.
This issue is more common during the first cold snaps of autumn when a fan that has been idle over summer is suddenly required to run at high speeds.
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.
Avoid the next call-out bill
A cover plan would handle faults like 669: no call-out fees, no surprise bills.
Affiliate links. We may earn a commission at no extra cost to you.