Originally Posted by Moonie

Look at which circuits are not working/faulty, then look at these circuits on a wiring diagram and see if they have anything in common (feeds, earths, fuses, splices in the loom etc etc).

Make sure all fuses are ok and all wires are connected to the battery (the small ones as well).

With the help of the wiring diagram and a testlight go through the circuits starting from the battery, the fuse, the component, the earth and all the wiring in between.