engine and drivetrain alternator wiring

[madpaddler]

Take a look at this pic. The only wires you see going to the back of this alternator is the 3 prong plug (top right) and the power to the top left stud. There is nothing attached to the lower stud...is this correct? My son just bought this 76, it won't start, getting power to hot spark coil, then to distributor, but nothing at the spark plug wire ends. Trying to figure this out with minimal knowledge. Battery checks out as good but engine turns over very slowly...

[baller908790]

There is supposed to be one thin ground wire? I know there should be one more wire but not sure if its a ground or not.

[madpaddler]

thats what I thought too, ground wire from the lower stud to engine grounding location?

[Stu]

Yes, there is a ground wire:

[madpaddler]

ok...so are we all saying ground from that lower stud to engine block...right?

[rms_sandiego]

Cranking slowly would be a battery or starter problem (or corroded ground strap from engine/starter to battery). It is probably not an alternator problem, and the lack of spark is also not likely related to the alternator.

If you are getting power to the coil, but nothing at the plugs, check the dizzy. What shape are the rotor, points, etc?

PS: Recharge the battery as a first step.

[baller908790]

Not the lower stud. Refer to STU's first picture is the small one.

[Stu]

ok...so are we all saying ground from that lower stud to engine block...right?

Mine goes from the small stud on the alternator (8mm nut, see photo) to one of the small bolts holding on the timing chain cover, front of the head (not the block).

[madpaddler]

This car was purchased with hot spark installed (don't think it ever started with it, looks brand new) so I'm trying to figure out what PO did. I have new set of plugs wires and rotor coming in from Blunt so I am trying to eliminate as many issues as I can while waiting for the parts...

[Guest_anonymous]

If the alt. has rubber mounts it needs to grounded. I ground from alt case stud to upper timing cover. If atl. is hard mounted in its bracket to the block, then no need to have a seperate ground. If ungrounded, current will find a ground. Mine found one through the hot wire to the frame rail, and torched my harness to the fire wall, due to a loose ground to the timing cover.

[rms_sandiego]

Hot Spark is a cheap pertronix knockoff. It is pretty reliable when it works, but can be bad out of the box. If the car never ran with the HotSpark module, then the first thing to do is to go back to points/condenser and make sure you get a good spark at the plugs.

As Proslack says, there needs to be a ground from the alternator case to the engine. Either through the alternator mount if metal, or a wire running from the back of the alternator case to the timing cover. Adding the wire is cheap protection if missing.

But from what you describe, the alternator doesn't sound like the reason for not starting.

[madpaddler]

I added the ground but it seems to make no difference, when my parts come in I'll update.

[mgben]

New issue, same title.. My new to me 73 2002 w/external regulator.. My Brown wire at the 3 wire connector at the regulator is melted and corroded. The Brown wire at the 3 wire connector at the Alternator is no longer there..frayed and missing up to the harness wrap.

The only other Alternator connector is the large Output wire with ring terminal, I did not notice an external ground to the engine. Could missing this have caused the problem?
What is the downside to having no Brown connection from the regulator to the alternator? I am thinking of an upgrade with internal regulator swap to get me out of this mess. Till then, should I replace / repair the brown wire? Need to know what would cause it to overload and meltdown before I reinstate the missing connection.

Thanks!

[71bmr02]

all of the solid brown wires on 02's are ground wires.  the brown wire should connect from the alt to the block. see one of the previous posts above.  although no stock, I cured all of my electrical ills by installing an early delco alt, 55 amp, changed volt reg to make it a one wire and no problems since.  needed a bit of b-y-e to fab the lower mounting bracket but no real problem.

 

G