I changed the thomostat the other day the filled the coolant back up and left it half hour to warm up and when it got to 90deg only the little fan kicks in so when it stoped I turned the a/c on and again only the little fan kicked in has any one any ideas how to test the big fan I unpluged the fan switch from the radiator and bridged it and again only the little fan kick in. Can any 1 shed any ideas as last thing I want is the car over heating thanks