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No power going to alternator after sparking with wrench

hooah212002hooah212002 Posts: 4
edited April 2014 in Chevrolet

My dad and I were doing a tune up on my car and one of us hit the alternator terminal with the ratchet and it sparked (yes yes, i know to disconnect battery now). I have narrowed it down to something not causing the alternator to get power because i have done the following:

Autozone tested the alternator twice and both times reported good. They also tested the battery to be good (it's only a few months old).

Tested the continuity of the wire that runs from alternator to battery and that is good. It read around .5 ohms. The alternator ground tested the same (negative battery terminal to alt housing).

The "L" connection on the wiring harness (I can link a picture if necessary, but i am on my tablet right now at work) has no power going to it regardless of key position (this wire requires 12v switched or something like that. Forgive my lack of technical jargon). The "S" wire, the one I think that goes to the battery, reads the same voltage as the battery.

The car runs fine when connected to my truck via jumper cables, but acts as one would expect when there are alternator problems.

I have checked all fuses in the fuse box, to include the 10a "GEN/BATT" fuse that I have been told is the alternator fuse. I have not found any to be bad. However, i have not tested any of the relays because i do not know how. I DID check the fuses with a multimeter, not just visually. Even though that fuse tested good, i chsnged it anyway to no avail.

There are no dash lights when the car is running, but they do all seem to work. They all illuminate when the key is "on".

I can not find any information source that says this model vehicle has a main large fuse (100+ amps) between alternator and fuse box for just this problem, but many other cars do seem to have that. If I am missing something, please tell me.

I do not know where to check from here. I have determined that the harness is bad, but maybe it's not? Where do I go now to check wire integrity? Is there a fusible link that i can't find? The wire harness that connects to the alternator is in a plastic sheath and I am very hesitant to tear into it searching for this gremlin.

Just for completeness' sake, the alternator is only putting out something like 8 volts when the car is running. I have tested this at the alternator terminal itself. There is zero difference in performance if i run it without the wire harness.

Thank you all for your help.


  • Your alternator should be putting out 14 volts, if not check your ground connection at alternator

  • @carfixer4 said:
    Your alternator should be putting out 14 volts, if not check your ground connection at alternator

    I have, I think, and it was fine. Perhaps i did not do it correctly. How would you suggest i do it?

  • For any lurkers, I fixed it. The problem was the alternator connecter. I tested the "L" connection and got no voltage. Today, I tested the corresponding wire right on the other side of that connection (while car was running) and got 5 volts. So I went to the dealer (none of the parts stores had one and I didn't trust a junk yard) and bought a new one. It had 4 wires, but the guy said it would be fine since on this alternator, the unused ports are completely unused so there would be no crossover.

    I installed it, crossed my fingers and BAM. 14 volts all around. I do NOT want to chase electrical gremlins ever again.

    I posted about it on the Malibu forums here: The thread Drunken Elvis references has a load of good information.

    Tight lines and rip lips.

  • steverstever Posts: 52,683

    Thanks for the update!

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