I did the continuity for the cables between the boiler and FCU using a multimeter. The cables are fine. I connected the boiler to alternative power from a wall socket (I changed the 13 A fuse to 3A) and am very happy to find that the boiler still work although I already paid £100 for the parts that I won't need any more.
I have not done the continuity test for the cables between FCU and main-power-supply. I opened the air-switch box in the main-power-junction-box and have no idea why the colour of cables is different (red, black green, don't spot any loose coonection) from the colour in FCU-switch-on/off (red, black, yellow&green). I guess there is another juntion hidding somewhere for the cables between the FCU and main-power-supply. The neutral cable may be loose there.
I do have to find a professional to solvent the problem now. Thanks for everyone. I do learn a lot from your reply. Maybe the information you gave is not rocket science truely it is very helpful may even save my life since I may touch the cables without understand the danger.
I have not done the continuity test for the cables between FCU and main-power-supply. I opened the air-switch box in the main-power-junction-box and have no idea why the colour of cables is different (red, black green, don't spot any loose coonection) from the colour in FCU-switch-on/off (red, black, yellow&green). I guess there is another juntion hidding somewhere for the cables between the FCU and main-power-supply. The neutral cable may be loose there.
I do have to find a professional to solvent the problem now. Thanks for everyone. I do learn a lot from your reply. Maybe the information you gave is not rocket science truely it is very helpful may even save my life since I may touch the cables without understand the danger.
