C3
FAULT CODE
Ideal
Air Pressure Switch Open
High Severity
Engineer Required
The air pressure switch is not closing when the fan runs. The boiler cannot confirm adequate combustion air flow.
Step-by-Step Fix Guide
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Step 1
Check the external flue for blockages
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Step 2
A Gas Safe engineer should check the condensate trap, air pressure switch, and fan
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Step 3 Engineer only
The silicon tubing connecting the air pressure switch may be blocked or perished
Gas Safe Reminder
Work on gas appliances must be carried out by a Gas Safe registered engineer. The steps above cover safe checks a homeowner can perform - any internal component replacement requires a qualified professional. If in doubt, always call an engineer.