If you have a chattering relay then it is probably not defective - it may well be the electronics that control the relay are causing it to make a racket - your relay is very probably an innocent party.
To arrange the supply of a replacement PCB on this site is not realistic - e-bay would be better and much quicker.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix home heating systems.