Right I've checked relay and fuses all ok, changed switches still same problem so i removed plug from fan switch and looped the connections fans kicked in straight away. so does that rule out the wiring? what could it be causing it they were ok last week. For time being I have wired to a switch not sure if this is right or not so ready to be corrected: on fan switch plug there are 4 wires (red/black, blue/black, black, black) ive run live from switch to red/black, earth to red/black and switch live to black fans work and fan switch lights up as it should but if i 've wired wrong i would like to correct!

cheers