When I put the Sprint engine in I also fitted a Pacet electric fan.
OK so far. I wired it up according to the wiring diagram but my friendly autoelectrician pointed out it needed an earth. Well it didn't say so in the instructions (I thought it must earth through the thermostat switch mounted to the car body) but sure enough connecting an earth got it working.
I could follow that the fan was "live" all the time but only came on when the thermostat "switched on" the earth.
Now, I thought it would be good to have a tell tale light in the car to show when the fan was on so I put it all in but now find that the light is on permanently with the fan off and goes off when the fan is on! This is far too difficult for me to work out.