9U
FAULT CODE
Worcester Bosch
Blocked Condensate / Condense Sensor
Medium Severity
DIY Check Possible
The condensate system is blocked or the condensate sensor is indicating a problem. Most commonly caused by a frozen external pipe.
Cold Weather Note
9U in cold weather is almost always a frozen or blocked condensate pipe. Thaw the external pipe and allow the boiler to self-clear before resetting.
Step-by-Step Fix Guide
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Step 1
Check if the external condensate pipe is frozen
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Step 2
Thaw with warm water if frozen
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Step 3
Wait 15 minutes for the boiler to clear the siphon
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Step 4
Reset the boiler
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Step 5
If the fault persists, call a Gas Safe engineer to inspect the condensate system
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.