Common Vaillant fault codes indicating a potential Printed Circuit Board (PCB) issue include F61, F62, F63, F64, F65, F67, and F70. The F61 and F62 are the most frequent, suggesting a faulty PCB or, less commonly, a problem with the gas valve. The F70 code specifically appears after a PCB replacement and indicates the need to correctly configure the new board's Device Specific Number (DSN). You should always contact a qualified Gas Safe registered engineer to diagnose and repair these issues, as attempting DIY repairs can be dangerous.
Fault Codes Indicating a Possible PCB Issue
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F61/F62:
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These are the most common codes associated with a faulty PCB, though F62 can also point to a defective gas valve.
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F63/F64/F65/F67:
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These codes generally indicate an electrical fault on the PCB.
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F70:
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This code appears on older EcoTec models (pre-2012) and signals that the Device Specific Number (DSN) of the new PCB needs to be correctly set after a replacement.
Why These Codes Point to a PCB Fault
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F61 & F62:
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These indicate issues with the gas flow or valve shutdown. While a gas valve can be the culprit, a failing PCB is a more common cause for these error codes on older boilers.
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F63, F64, F65, F67:
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These errors are direct indicators of electrical problems within the PCB, possibly due to age or component failure.
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F70:
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When a new PCB is installed, the boiler needs to "learn" its specific settings, and this code means the DSN hasn't been correctly entered or adjusted.
What to Do
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Reset the Boiler: Try resetting the boiler by locating the reset button (a flame symbol with a cross through it). The fault may briefly clear, providing time to arrange a repair.
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Call a Gas Safe Engineer: Because the underlying issue can be dangerous and involves gas, you must call a Gas Safe registered engineer to diagnose the problem properly.
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PCBs & Gas Valves: A Gas Safe engineer will test the gas valve and the PCB to determine which component is at fault.
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Configure New PCB (if F70): If the F70 code is present, the engineer will need to enter the correct DSN into the new PCB to pair it with your boiler.
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