New to the forum i have a 1968 F350 390 custom cab with a 360 v8 that I'm helping a friend out with it has a new alternator and starter solenoid to alternator wiring harness when placing negative cable on battery i am getting some crazy arcing action i can't find any rotten wires and ideas wheres else to look would be great .

 

Welcome aboard. First, make sure you have battery polarity. Negative terminal to ground on block. Positive to solenoid, not stater.
Come on bak in and we will help you through the troubleshooting.
Do you have a multimeter and do you know its use?

 

The three wires on the Alternator should be pretty straightforward.
BTW the wiring harness to the Alternator doesn't go to the Starter... one connection is to the hot side of the Starter Motor Relay, but nothing goes to the Starter Motor itself.



The Alternator is grounded through wire #26A, which provides ground for the Voltage Regulator's case via Wire #26, which then provides a ground via Wire #26C to a pin on the Field Relay Connector, and then continues on via Wire #26B to a pin on the Voltage Regulator Connector. Grounding for the case occurs when one of the Voltage Regulator's mounting screws holds the wire's connector between the VR case and the sheet metal it is mounted on. Wires #26, 26A, 26B and 26C are all Black with a Red stripe.

+12VDC is supplied to the Alternator via the Battery Terminal connector of the Starting Motor Relay (which should have a heavy battery cable connected directly to the + terminal of the Battery). The wire for the Alternator is a separate wire, but it is connected on the same stud on the Starter Motor Relay as the + Battery cable. Wire #38A provides +12VDC to several other places: Wire #37 (which routes through a couple of connectors, but finally) provides power to the Ignition Switch; Wire #654 (which connects through a 4A fuse and some connectors, but ultimately) provides half the signal to the Ammeter Gauge on the Instrument Cluster; Wire #152, which provides power to the hot side of the Field Relay and finally, provides, via Wire # 38, +12VDC power to the Field of the Alternator. Wire #37 is Black/Yellow stripe, Wires #38 and 38A are Black and Wires #152 and 654 are Yellow.

The remaining terminal on the Alternator is what provides the raw, unregulated +12VDC power out. This is applied, via Wire #35, to a pin on the Voltage Regulator Connector. Wire # 35 is Orange.

If you have a wiring harness that is molded in order to match up with the three studs on the Alternator, you've probably hooked up the other end (the end without the molding) wrong somehow. Use a multi-meter in the "Ohms" setting to test the harness for correct connections before you try to re-install it. If the harness seems wrong, send it back and get a different one.

After an arcing-sparking session, it's a good idea to disconnect the battery and recharge it before trying to start the engine.

 

Thanks for the advice when i got involved in helping with this the negative from the battery was on the starter solenoid and the positive was going down to the block where the ground is coming off the alternator and on the other side of the starter solenoid was a wire going down to the starter.

 

Thanks for the advice i will run through and check it out, the harness is actually from starter solenoid to alternator not the actual starter motor i left out the solenoid part in the original post.

 

I am fairly certain that the negative and positive wires were switched now that you mention where the positive goes to, when i got involved the truck had a red battery cable coming from engine block and a black cable coming from starter solenoid i went off colors not tracing back like i should have wire defiantly isn't my specialty. Thank you very much!

 

Lando, if the battery was installed backwards and the alternator was properly wired, I am sorry to tell you that you blew the diodes in the alternator and you will have to replace it.
The battery will have - and + marked at the terminals. It is very important that you get it correct.
You may also have problems with the voltage regulator and any aftermarket solid state devices that were on when the battery was reverse connected.
Good luck.

 

Don't feel bad about making mistakes, they are wonderful ways to learn. You should see some of the flubs I've been responsible for *sheepish*.
The bigger issue is to make sure nobody gets hurt.