5C
FAULT CODE
Viessmann
Outdoor Temperature Sensor Open Circuit
Low Severity
Engineer Required
The outdoor temperature sensor wiring has an open circuit or is disconnected.
Step-by-Step Fix Guide
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Step 1
Check the outdoor sensor cable for damage
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Step 2 Engineer only
A Gas Safe engineer can test and replace the sensor or wiring
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.