p38 heater fan problem

Hi all can anyone help iv'e tried everything to fix this problem, the problem is that the blowers wont work iv'e replaced the blower motors-
it's not that, iv'e replaced the control panel not that.ive replaced the relay not that. now when i tried to change the control panel and i pulled the middle plug out the blowers started to work and when i plug it back in they work as they should. (and the book is on the display) help please!!!!

Did you check the fuse board under the relays for burning??? That was my problem. Took the fuse box out and could see coroded wires which kept blowing the relay, cleaned these up and voila.

thanks for that will try it and let you know how i get on.