Grant Vortex Combi 36e Power LED flashing. No heating or hot water.

[EddieDuck]

Hi. Our Grant oil fired combi boiler (installed in 2014 and regularly serviced since) has developed a fault today (heating and DHW were both working fine yesterday).

The main power rocker switch light is on, but the Power indicator LED flashes continuously (at a bit faster than a 1 second interval). No other indicator LEDs are on. The heating mode switches are both set to "Constant". The boiler doesn't respond to demand for either hot water or heating (we have 2 CH circuits, underfloor heating downstairs and radiators upstairs). Neither the Burner nor the Overheat lockouts have been triggered, but I've pressed to reset them anyway. The pressure was a little low (around 0.5 Bar), but I've topped it up to about 1 Bar. The Low Pressure LED also had not been triggered and topping up the pressure doesn't seem to have affected the error state.

Is there anything else that I can and should check before investing in a new PCB? And is the MPCBS96 PCB (post Sept 2008) the correct PCB? It looks identical from the photos, but the numbers on the label on my PCB are different (M611256 GRANT VORTEX 428900 ML A04).

Hoping someone can provide some advice! Thanks in advance.

 

[Exedon]

Have you actually checked power is getting to board?
The rocker switches are known to fail (we never attempt to use them)
What model is your boiler? Grant do make more than one.
Has your boiler 2 small boards or one large one?

 

[EddieDuck]

Thanks for the reply.

No, I haven't checked for power to the board, but I assumed (I know, never assume) there must be power for the Power indicator LED to illuminate (the one on the front panel, not the rocker switch). Our service guy mentioned the rocker switches were unreliable, so we always use the switch on the fused spur to power off. But nothing was changed before the failure. It just expired quietly overnight. Or maybe first thing in the morning.

It's a Grant Vortex Combi 36e and it has one long rectangular control board. I'm just hoping someone can tell me if this sort of failure could be caused by a faulty sensor or wiring, or some external input, or is the board the first thing to change.

Thanks again.

 

[EddieDuck]

Update:
Sharing in case it's useful for anyone else who sees this seemingly quite unusual symptom of a non-functioning boiler with just the flashing Power LED on the front panel. The very helpful people at Grant's UK technical support contact line (e-mail) diagnosed that the flashing Power LED suggested that one of the relays on the PCB was "cooked" (their term). I obtained a new board (part number MPCBS54E) and swapped it out and the boiler is working as it should again.

 

[Exedon]

I've always found Grant technical excellent in stark contrast to most other oil boiler manufacturers.
The combi board is known to fail but nearly always after getting water on from careless venting of heating pump.
I've known them survive for some time after getting wet but then fail.