
Originally Posted by
joshua43214
You really only have 1 wire to worry about if I am reading you right. The positive battery cable is about the diameter of the tip of your pinky. If my memory is right, it runs from the battery to the alternator, then to the starter. I can't remember where the jumper lug wire comes from. Verify that the big power wire on the back of the alternator is tight, or even remove the nut and check to make sure the wires are making good contact.
Do a resistance check on the positive wire from the battery to the starter, if high resistance or open circuit, go from alternator to battery then alt to starter. Battery cables do fail with age, though its rare on BMW's. If you have no open circuits, you need to do a voltage drop test, this is really the only proper way to diagnose a battery cable. using a volt meter, hook the neg terminal to the positive battery post. connect the positive terminal to the starter post. crank the engine, the voltage you see on the meter is what is knoot nbeen able to do wn as voltage drop, or in other words, the number of volts lost accross the circuit. the acceptable voltage drop depends onthe type of circuit. For battery cables the normal standard is .1-.5 volt drop is ok, I feel anything over .2-.3 is bad.
Chances are you wont have to do a volt drop test, for what you describe a simple visual inspection of every connection the battery cable makes and maybe a resistance check should suffice. Just follow the big wire under the seat and under the hood.
Good luck, let us know what you find.