Due to a problem with my radiator cooling fans not working, I have cut the cables to them and hard wired them through a switch and 2 relays (one 40A relay for each fan) On testing the fans with my ammeter I find that each fan is taking about 25A - 30A to work. Is this normal?

 

That's one hell of a current for a 12volt fan! At 30A. that's 360watt! Or for two 720watt!!!
If the fans seem to be working normally, your meter is prob. inaccurate.

Diesels generally don't need much cooling of the engine as compared to an equiv. petrol, being much more efficient at fuel burning and turning the generated heat into power. Apart from a blocked rad. fault when I first got mine, it never switches on the fans.

Leedsman.