F.85
FAULT CODE
Vaillant
Temperature Sensors Incorrectly Fitted
Medium Severity
Engineer Required
The flow and return temperature sensors appear to be fitted the wrong way around, giving inverted temperature readings.
Step-by-Step Fix Guide
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Step 1
This usually only occurs after service work or boiler installation
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Step 2 Engineer only
The engineer who last serviced the boiler should check sensor positions
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.