Yesterday I ordered a Escort Cosworth fan switch for my Sapphire 4x4, as I don't like the way the fans are working as standard. I also have the Escort fan switch on my 2.9 24v. On that car I have used a relay from a bug eye Scorpio to switch both fans in series (6V to each fan), so they only run at a low speed at the first temperature level of the switch (on at 95 degrees). At the second level (on at 100 degrees) both fans are switched in parallel (12V to each fan), so they run at full speed.

Normally the fan switch is located in the supply (hot) side of the radiator. One other thing I also changed on my V6 is to have the temperature switch in the return hose from the radiator. That way the fans only switch on if the return water is still too hot. On the V6 this seems to work perfectly.

The YB also has the switch fitted to the supply side of the radiator. To me this just does not make sense. Why would you want to switch the fan on when the water to the radiator is too hot? The radiator may still be able to cool it enough by the natural wind from driving, so there would not be a reason to switch on the fans. Only if the return water is still hot the fans should switch on. Or am I missing something here? As I can't believe Ford would have gotten this wrong...