H.01-.05
FAULT CODE
Baxi
Flow/Return Temperature Difference Too High (200/400)
Medium Severity
Engineer Required
On Baxi 200 and 400 series boilers, code H.01-.05 indicates the temperature difference between flow and return is too high — sensor error or insufficient circulation.
Step-by-Step Fix Guide
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Step 1
Check system pressure and bleed radiators
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Step 2
Ensure all radiator valves are open
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Step 3
Reset the boiler
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Step 4 Engineer only
If fault persists, call a Gas Safe engineer to check pump and sensors
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.