Ferroli 39807690 Honeywell MF03.1 PCB

The Ferroli 39807690 is a printed circuit board carrying the MF03.1 designation. It is the control board for the appliance, handling the electrical sequencing that governs ignition, burner modulation, pump and fan operation, and the safety interlocks that shut the appliance down when a fault is detected. It is supplied as a Ferroli spare and is listed under the standard water heaters category.

• The appliance fails to fire or drops into lockout shortly after a call for heat or hot water.
• No display, blank display, or a display that flickers and resets during operation.
• Repeated fault codes that clear on a power cycle and return once the appliance runs.
• Pump, fan or diverter outputs not energising even though the demand signal is present.
• Visible damage on the board: scorching, discoloured tracks, bulged capacitors or a blown fuse that fails again after replacement.

• Read the part number from the existing board and match it to 39807690, including the MF03.1 marking, as boards for the same appliance family can differ.
• Check the appliance data badge and serial number so the correct variant is identified before the board is removed.
• Inspect the wiring harness, plugs and earth connections while the board is out; damaged connectors can mimic a board fault.
• Work on the appliance electrical supply only with the isolating switch off, and follow the manufacturer's wiring diagram when refitting.