Yes rewire the fans!

The original wiring was sub standard from new, leave alone now!

In your case it sounds like a short as the fans do not run unless they are needed, in traffic etc (I woulden't keep replacing the fuse as it's blowing for good reason) but there is no point in wasting time trying to trace the problem as they need rewiring anyway!

If you do a search on here there are plenty of threads with diagrams, you can either buy looms pre made or DIY.

Another weak point is the fuel pump wiring, with age it builds resistance, so the fuel pump cannot draw the power via it that it needs, this can lead to an engine meltdown, again a rewire is the remedy or you need to check the voltage present WHEN under load.

Martin