Low
LED3 on PCB 37 on Ideal Classic FF

This light is actually a positive signal showing that your boiler's internal electrical fuse is working correctly and the control board has power.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

What the manual says

Manufacturer manual

Lit confirms the fuse is good on PCB 37.

From this model's manual
Verified against the Response Ff80 installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

What causes this fault?

This light is not actually a fault, but a status indicator showing that the boiler is receiving electrical power. It confirms that the internal glass fuse is intact and the circuit board is functioning as intended. If your boiler is not working while this light is on, the issue lies with a different component or external control rather than the power supply.

DIY fix possible

No action required as this light indicates a healthy electrical connection to the board.If the boiler is not working despite this light being on, check that your room thermostat is turned up.Ensure the main power switch to the boiler is in the ON position.

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