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Big 3 problem (not the normal) 2005 Grand Prix

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  • Big 3 problem (not the normal) 2005 Grand Prix

    Hey all,
    I hate to start out my first post with a long question, but I really think I screwed myself this time. I have a 2005 Grand Am base model and I have attempted a big 3 upgrade w/ replacing the factory wires (mistake.....)...

    I ran a 1/0 gauge wire from the battery to the fuse box under the hood, replacing the 4 Ga. factory wire.

    The factory terminal had 2 positive wires coming from it. One for the fuse box and one for the alternator (or so i though). I could not locate where the second wire went but I could get a power reading at the alternator wire when I placed the second terminal wire on the battery. Hence my thinking it disappeared under the engine and reappeared at the alternator. So I though I could remove the wire from the alternator and not have to be bothered with the other side and just tuck it away sealed off somewhere. sooo....

    I replaced the 8 gauge alternator to battery wire with a 4 ga and used a 120 amp breaker at the battery (mistake #2 I keep blowing the breaker).

    The ground terminal had 3 wires 2 8ga. and one 22ga. One went to the chassy, the other to a location unknown. These wires ran through a inductive trigger of some sort. I removed the chassy wire and cut the 22 ga. and linked into the new terminal and left the other engine ground unhooked as I would not need it with the wire upgrade.

    I ran 1/0GA from the battery terminal to a 2 legged body ground I fixxed to the sheet metal on the firewall (cleaned bare under the legs) and ran 4Ga. from the terminal to an engine ground on the alternators case that also grounds the engine.

    I also ran 4Ga. from a bolt on the transmission to the chassy with another 2 legged grounding block.

    At this point the car would run all electronics with the key on, but would not start. I then discover the red wire I have tapped off and tucked away was for the starter (battery--->starter----->alternator) and I have no room on my new terminal for another 8Ga. wire. As I have a 4Ga run for a 1000 watt kicker mono block in the trunk.

    To test the circuit I re-connected the wire I removed from the positive lead on the alternator and the car started. So Now I have a live 8ga. wire tapped off and tucked out of harms way.... and I'm not happy about it.... but until I can track the wire down all the way top the starter, I am stuck with it.

    Also the inductive pick-up (I have learned) controls charging to some extent and now I am thinking the 1/0Ga. wire ran though the pick-up might not be a good thing. It should be the same amount of power though the cable, but I don't know for sure.

    I have a terminal that displays voltage and when the car is started it hit 15.4 volts at the terminal.... I am thinking the alt isn't regulating charge due to incorrect values from the inductive pickup (isn't the alternator regulator a off/on type of switch and not a true voltage adjustable regulator?).... or the cheap e-bay terminal isn't reading correctly.

    Also I have to remove that dead second ground wire from the car, but right now it is taped and tucked away.

    I hate doing such guess work but I could not run my system without horrible lights dimming and even some poor engine performance from weak spark.

    I read and re-read all the posts I could find about doing a big 3 upgrade and I have yet to see anyone run into these problems.

    Any help would be welcome and yes I understand I have a lot of learning to do when it comes to this..... the 120 amp breaker will tell you
    2005 Pontiac Grand Prix
    1000.1 Kicker
    2 - 12" l5's in port tuned box.
    I-phone and GM pac supplies the tunes...
    Car-Puter to come after other issues resolved....

  • #2

    I am going to have to print your saga out and read it a few times, just to get some kind of grasp on what you did. No wonder you haven't gotten any replies, yet.

    Only you really know. No unkindness meant, here, only sympathy for what appears to be a real dilemna....

    In the past, I got myself into such situations by not tagging wires or making at least some rudimentary sketch / schematic of before / after. Not doing that can be a real killer.

    You may have guessed that the only way out may be going back to where you were: put it ALL back as stock, then take little baby steps to do your mods. From your narrative, you made several assumptions and guesses. Not good.

    Have you got a factory service manual with the wiring diagram? Those things are good in one respect, showing wiring colors, gauges, locations. But there are always mistakes, sometimes pretty serious ones...

    Sounds like all of those added grounds (alternator case, xmission hsng, etc) could definitely be causing a serious ground loop. A quickie might be to pull those off and see if situ. improves.

    To not go on too long, one last suggestion: when this tech gets confused or lost, I look at a good working unit of what I'm working on to compare wiring, component placement and such. Now, you might have to go as far as the local wrecking yard, but you need to get things back to the way they were ASAP. Looking st someone else's ride or wrecking yard car could really help - but remember that it will need to be same yr, make, model....otherwise differences could make things worse.

    Take it slow. You don't need a fire.

    Blessings on your work.

    Happy CarPC'ing!


    • #3
      its sorted out

      Yeah, I got it sorted out.
      At the time I wrote the post I was upset and tired. I did a whole lot of research and discovered the inductive pick-up just monitors state of charge, so changing to a larger wire would not effect the reading what-so-ever.

      The ground wire and positive I cut have been added back correctly, one was just the tranny ground and the other was the charging wire the was in series with the starter...

      As far as 15.7 volts....its fine... My alternator regulates voltage in 5 stages and can go as high as 24 volts if needed @ 120 amps.

      Basically I was right in how I planned my wire, I just didn't plan on the starter being in series with the alternator. From a design stand point, it didn't make much scene to me why GM would route a charging wire so long and so small of a gauge on a 120 volt alt. but, I'm sure it saved them a nickle or something.

      Anyway, all is good.... no ground loop and normal charging keeps me around 14.3 to 14.7 volts.
      At full tilt (all lights on wipers going and system running hard) I still see over 13 volts.....

      good stuff....
      2005 Pontiac Grand Prix
      1000.1 Kicker
      2 - 12" l5's in port tuned box.
      I-phone and GM pac supplies the tunes...
      Car-Puter to come after other issues resolved....