yeah the back-powering bit is what i'm worried about, like if only 6v comes out of the blue wire and i connect it to the green wire which could be throwing out say 12v and end up sending 12v back up through the blue wire

so yeah couple of relays hey, great idea, will have a play with the multimeter and see what its throwing out of each wire once they cut in or when the a/c is switched on

wish i hadn't just bought a new foz radiator last year, would make it easier to just go and buy an all ally gc8 ones that i could just bolt the gc8 thermo's onto & bolt it in be done with it LOL