My radiator fan started cycleing on and off and sometimes it wouldn't come on at all . When I wire it up direct , It runs fine . I have my fan running thru a relay , so I replaced the relay and checked all the related wireing and can't see any problems . I think I have the problem narrowed down to the thermostatic switch . I ordered a new one and will go from there . Has anyone else ever had a themostat switch go bad or am I the only one that has **** like the happen . Also does anyone know how to test one of these switch's . How about it Neil