stand alone voltage control and big 3 upgrade?

Discussion in 'GM Electrical Tech' started by Pikey, Feb 1, 2013.

  1. Pikey

    Pikey Moderator

    I have a 2005 yukon xl and am looking at doing a big 3 upgrade. My question is, there is a box on the negative battery cable of my truck. if I do the big 3, do I need to run the grounds thru this device? I think it is for the Stand alone Voltage Control, that is designed to adjust alternator output as needed and keep the battery charged at 80%. Will running the grounds away from this effect my truck's charging system?
    Last edited: Feb 1, 2013
  2. Jamm3r

    Jamm3r New Member

    A photo might help. Usually there's a red plastic plastic splice box in the positive cable where the cables for the alternator, starter, and battery come together.
  3. Pikey

    Pikey Moderator

    Here it is. On the other side it has GMSAVC written on it along with a part number. From the little research that I have done, it does not look like a good idea to go around it. As you can see there is not much room in the clamp for another wire. Maybe I will just clean the grounds for the battery. Then, install new grounds for the engine to frame and cab to frame. I just noticed in the pic how you can see the salt from the roads creeping from the wheel wells. Looks like it will be time for another engine detail soon!

  4. Pikey

    Pikey Moderator

    anyone have any ideas?
  5. Conlan Rose

    Conlan Rose Super Moderator

    [MENTION=50075]SurrealOne[/MENTION] might know, his truck is just a year older than yours and he did a major electrical upgrade.
  6. Pikey

    Pikey Moderator

    The 2004 trucks that I looked at did not have it. Maybe his did. Guess we will find out
  7. SurrealOne

    SurrealOne Former Member

    No box on my negative connection -- just the standard red plastic box on the positive connection.
  8. Toymyster

    Toymyster New Member

    That box does not connect to ground. It is only clamped to the ground cable. GM calls that box the Generator Battery Control Module. From what I gathered, it acts as a voltage regulator. If you are just looking for a ground, anywhere on your engine or chassis will do.
  9. Enkeiavalanche

    Enkeiavalanche Moderator

    What are you doing that you need the Big 3?
  10. Pikey

    Pikey Moderator

    I never said that it was connected to ground. My post clearly states that it is clamped around the wire. I am concerned that if I run the big three and basically bypass the module then I am not going to have the correct alternator output.

    - - - Updated - - -

    I want to do it because I have some future mods in mind. I also get some severe dimming of lights when I roll the windows up. The battery and alternator are brand new.
  11. Jamm3r

    Jamm3r New Member


    Thanks for the photo.

    I am unfamiliar with the details of the 2005-up voltage regulators but I know a thing or two about batteries and charging controls and can guess at most of it.

    What you call the "box on the negative battery cable" is a current sensor. Its purpose is to measure the current (amps) to and from the battery. It's one of the pieces of the puzzle that the computer has to have in order to accurately determine the ideal output voltage to set the alternator for. Battery temperature and the amount of time since the engine was started being the other important variables.

    So here's the scoop. See how you have two wires that both go from the - battery terminal and then through the ring of the current sensor? The large one goes to the engine block somewhere, and the small one goes to the sheet metal of the chassis, usually on the fender or to part of the radiator support structure. If you want to do a big 3 what you want to do is replace those with a single wire going from the battery terminal, through the ring, and to the engine block --- and then attach the existing little wire, the end of it that used to go to the - battery terminal, to the big wire by soldering a running splice, like this:

    Engine ground------------+-------O------- (-)battery
    .. . . . . . . . . . . . |
    .. . . . . . . . . . . . +---- fender/radiator support

    Where the "O" is the sensor.

    You'll find that without the little wire having to fit under there you can upsize the wire by at least a couple of sizes. Might want to take it to the parts store and test fit it since insulation thickness can vary from one wire type to the next.

    You make the running splice by stripping about 1-2" of insulation from the part of the larger cable where the splice will go, then wrapping the (stripped bare) end of the smaller wire around it 3-4 times. Then solder it with good, rosin-core, tin/lead solder, and wrap it with tape. A 300W soldering iron or gun works best but a torch will work too as long as you're careful not to overheat the joint.

    The current flow through the sensor with this setup will be the same as what you had with stock so the performance of the charging system will be exactly the same. In essence you want to run all the ground-to-battery connections through the device, but not any other grounds.

    ETA: Dots. Ignore the dots in the diagram, they're there so the forum software won't change the spacing
  12. Enkeiavalanche

    Enkeiavalanche Moderator

    Sounds good to me...
  13. Pikey

    Pikey Moderator

    Wow, I just saw this post! Thanks [MENTION=53334]jamm[/MENTION]3r that makes complete sense.

Share This Page