The other day I noticed sitting in traffic the fan was not cutting. I tested it at home by running the car stationary for ages but the temperature gauge never went over normal, but the fan never came in. So I've change the fan switch that screws into the radiator and now it cuts in when I'd expect it to. I've got the other problem now of the fan on too much. I don't think that it's overheating (though not positive) and have changed the thermostat and water pump as I thought that they were the problem. Also I have removed the radiator and made sure that water cold easily flow through it. The big problem is that the fan stays on when you park the car and the other day managed to flatten the battery! Could the new fan switch be faulty? If so how do I test it? Or is there something else I'm completely missing?