I have a Vaillant Turbomax 283E. When I switch it on the lights on the front panel start to light up but locks out and trips the consumer unit RCD. I have replaced the PCB and checked the electrical connections are tight at all obvious connections through to wall isolator box. If it is any help. If I disconnect a lead at the pressure differential microswitch the RCD does not trip but of course the boiler does not light.

Any ideas? Thanks.

Paul, July 2008

If you are interested, I have continued to try to find the fault. At the moment everything is working again. I think the solenoid wiring inside the solenoid casing(which I cannot remove)is faulty. I separated the wires, the earth to the left and the RH black wire to the right and everything is go. If this turns out to be a fix I will get a new solenoid.

Paul, July 2008

Thanks T,

The diagnostic lights show these to be ok, though I take note it could still be them. I have now changed the main PCB, the differential switch with micro switch. The overheat reset and now having spent over £100 it is time to get British Gas in who say they will fix it for £192. I can actually get the boiler running normally for about 30 seconds before the RCD goes again.I feel a little sick I have not been able to get to the bottom of this.

Paul, July 2008

could be the fan, pump, or gas valve solenoid causing this

T, July 2008