I believe I've isolated the problem to the alternator because with the big red cable disconnected at the alternator the shorting out and sparking at the battery doesn't happen. I believe the alternator is hooked up as it should be and as it was. There is a push on female connector(red wire)to the back the alternator. On the positive post are the cable from the starter, and a small brown wire from the a very small black plastic box an the back of the alternator. The alternator is grounded to the block by another separate heavy blue wire. There are three other wires that come off the back of the alternator and go in a harness together to a small metal box behind the headlights.

Doug -

I note that you list two Volvos. I am assuming that the one you worked on is the 1981 242, since you describe an alternator with an external voltage and the 1986 is internal.

I am going to use the 1977-78 the Wiring Diagram Manual, because I think it will be close. There may be some differences though, so double check everything.

There is no brown wire to the alternator. What is shown is (1) the fat red one that carries the charge to the battery via the starter. (2) The thin red wire that hooks to the back of the alternator, (3) a 3-wire harness that goes to the voltage regulater (that metal box behind the RH headlights), and (4) a ground wire that usually connects from under one of tha alternator frame bolts to the rearmost of the bolts holding the bracket on to the block.

That leaves you with a "spare" brown wire, right?

Looking at the various diagrams, I can't see a brown wire at the battery + terminal. There is a smaller red wire that goes to a connection box that is mounted on the same rail as the headlight dimmer relay. (BTW that box lid opens by moving it vertically.)

There is a brown wire that runs from the starter to the ignition coil resistor. If your car has one of those resistors, it will be mounted near the coil. It will have at one end two brown wires, one directly to the coil, the other goes into the harness and turns up connected to the starter at Terminal #16. The other wire from the resistor is blue and runs to ignition control module over by the W/W fluid reservoir.

Check that brown wire and post back, OK?

Good Luck,

Bob
:>)