Alpha Printed Circuit Board CD25/28X 1.027959

This is the printed circuit board (PCB) for Alpha gas boilers in the CD and 12S ranges. It is the main control board inside the appliance, handling ignition sequencing, fan and pump control, temperature monitoring and the safety interlocks that shut the boiler down when a fault is detected. Alpha supplies it as a direct replacement board for the listed models, under part number 1.027959.

• The boiler locks out and the reset button has to be pressed repeatedly, with no obvious fault elsewhere.
• No response to a call for heat or hot water, even though the thermostat and programmer are working.
• The display is blank, flickering or showing intermittent or scrambled information.
• The fan, pump or ignition sequence does not start, or starts in the wrong order.
• Random lockouts and error codes that change between visits and cannot be traced to a sensor or gas-side fault.

• Check the GC number on the appliance data badge against the list above, as the same boiler family uses more than one board revision.
• Confirm the board currently fitted carries the previous number 1.024826 or an alternative number listed here before ordering a replacement.
• Boards are model and revision specific, so match the appliance model and variant (including LPG versions) rather than relying on the boiler range alone.
• Inspect the wiring harness and connectors for heat damage or corrosion while the board is out, as these can cause the same symptoms as a failed PCB.