F.76
FAULT CODE
Vaillant
Primary Heat Exchanger Overheating
High Severity
Engineer Required
The overheating protection on the primary heat exchanger has activated. Often caused by scale buildup, low flow rate, or a failing pump.
Step-by-Step Fix Guide
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Step 1
Turn off the boiler and allow to cool
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Step 2
Do not repeatedly reset
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Step 3 Engineer only
Call a Gas Safe engineer — the heat exchanger and pump need professional inspection
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.