other point of failure could be the relay (big green one at the side of the battery) they actually switches the fans on from off to lo to high. mine was full of water and the inners had rotted out leaving only the high speed working whihch in turn caused the temp to rise up before the fans kicked in. i eventaully replacee the relay and fitted a 2wd stat so that the fans came in at high speed straight away at the lower setting.