Help needed - malfunctioning Main Combi Eco 25

[MalcolmR]

The boiler which works fine for the hot water, isn't running the heating. It stopped working yesterday, I tried the usual power off/on, reset etc. Just as I was taking the cover off, it burst into life. Today it stopped working again, and I can't resurrect it this time.

The thermostat is set to maximum, the timer is set on override. The fan and burner come on when I'm drawing hot water, the pump gets hot too. It's only 15 months old, I can't find any loose connections. It doesn't even try to run until a hot tap is turned on.

I've found the manufacturers installation guide online. Following the fault finding chart in that leads me to "Replace the PCB". Is this likely in a 15 month old boiler? I note that the same Siemens PCB is used in a number of different boilers, is it likely to be unreliable, or am I just unlucky?

 

[ctp]

link out the heating connection inside the boiler to test the function of any external electrics, its inside the cover on the l/h side next to the mains connection.

 

[MalcolmR]

link out the heating connection inside the boiler to test the function of any external electrics, its inside the cover on the l/h side next to the mains connection.

Sorry, I don't quite understand you. The mains comes in to a terminal block, then goes off to the rotary Reset/CH+HW/Off/HW switch.

Do you mean that I can short out the electronic timer connections, or just disconnect it?

 

[Steady]

No he means that inside the boiler will be some terminal blocks. Three of these will take your incoming live neutral and earth. There will be two more terminals which would have had a small link wire between them when boiler was new. This link wire would have been taken out and these terminals used to connect to your room thermostat/external controls. You need to temporarily disconnect these wires and restore that link then you can eliminate the possiblity that it is your external controls(not the boiler) which are malfunctioning.

 

[ctp]

you need to replace the factory fitted link on the connection strip,the boiler comes without the clock when new ,or just link out the heating call clock wires (not the mains connections on the clock).

 

[MalcolmR]

Sorry, I was a little confused. I have no external devices. I have found these connectors, the factory fitted link is still in place. I have a timer fitted into the boiler fascia, the thermostats are on all the radiators.

 

[ctp]

bypass the clock electricly not just on the overide selector on the clock.

 

[MalcolmR]

I have unplugged the timer from the PCB, still no joy.

 

[ctp]

have you linked the call wires on the clock .....

 

[MalcolmR]

Do you know which they are? I can't find it in the manual.

 

[ctp]

on the clock there are two power leads ,blue/brn and two black ,connect the blacks together.switch the boiler off whilst doing this

 

[MalcolmR]

Sir, I owe you a large drink. The timer it was. My family will sleep warmly tonight.

 

[ctp]

your welcome,regards colin.