F.84
FAULT CODE
Vaillant
Flow and Return Sensors Exchanged
High Severity
Engineer Required
The flow and return temperature sensors appear to be reading the wrong values, suggesting they have been swapped or have both failed simultaneously.
Step-by-Step Fix Guide
-
Step 1
This usually occurs after service work
-
Step 2 Engineer only
The engineer who last worked on the boiler should check that both NTC sensors are in their correct 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.