Potterton Suprima Red Flashing Reset Light

Was called by a gentleman today who I had done work for in his previous house. He had moved to a new property but had been having trouble with the boiler and thought it needed servicing. I visited to service the boiler and look into any issues he was having with the boiler.

The boiler was a Potterton Suprima and the gentleman was regularly having to press the reset button as the red light was often flashing and the boiler was not running. The fault had been happening for the past six months but was gradually worsening. There didn't appear to be any set pattern as to when the boiler would lock-out and the red light would start flashing.

Pressing the reset button would get the boiler going again and it would carry on working for a few days without issue. However, being the winter, the problem was getting more of an issue as the gentleman would get up to find he had no heating or hot water just when he needed it.

I looked over the boiler and serviced it at the same time. The electrode looked to be clean and have the correct spark gap. The ceramic on the electrode looked to be in good condition. The ignition lead was not the original and it may have been that both the electrode and lead had been replaced in the past. The old electrode lead were prone to breaking down and causing ignition problems, they are sheathed with red insulation. The new electrode leads are sleeved in clear plastic, and thicker black plastc where the lead passes through the case.

It is a possibility that the boiler was overheating due to a fault with the thermistor and/or overheat thermostat but in my experience these generally fail and the boiler will lockout every time it runs. I have also experienced the gas valve failing to open which prevents the boiler from lighting. Again, I have found that this usually fails and cannot be resolved through pressing the reset button.

I dropped the panel down to reveal the PCB and could see that there was some signs of scorching to the PCB near the centre of the board. This is common on these PCBs and I expect is related to the lockout issue. There is usually a manufacturer's sticker on the PCB either on a relay or a semiconductor chip which has a sate code on it. This particular PCB was made in 1998 and has lasted well. There is also a date code in the bottom right-hand corner of the data plate, which again was 98, indicating that it was the original PCB.

I replaced the PCB with the new upgraded PCB kit, 5111603. This comes with a new PCB, housing, wiring loom and ignition leads. After fitting this part the boiler has been working well with no issue for the past fortnight.