Electrical Power issue

Discussion in 'General Chevy & GM Tech Questions' started by ColonialRovers, Sep 30, 2009.

  1. I just picked up a GMC Suburban K2500 6.5 Diesel with 42000 miles. It's your base truck with good hauling power, I believe it's an Ex County Truck from Florida.

    Here is my problem, the Voltage gauge hardly goes over 11 volts, but when you put it on a meter it's says 14volts. When I was driving home from Florida to NC, The gauge kept going lower and lower finally getting to the 9 Volt range. So I pulled into Brunswick Ga to get gas and it won't start. Got jumped by AAA, who from his jump box said it was charging. About two miles from there on I95 the truck starts to run poorly, the transmission is slipping, so I pulled over on a Truck weight station, open the hood and twist the positive cable on the passenger side battery, the truck while still running, springs to life. So I drive further and pull over for the night. It starts the next morning and I make it back to NC. I take it to a local GMC for a few other issues I saw on the drive home, the Service Engine Soon light would come and go, leaky A/C into the cabin.

    I get it back yesterday and it shifts like it's low on fluid, hits real hard. Today I purchased new screw in battery poles, replace three of the four, clean the connections tighten that loose cable and while driving it around town it drives Ok, like it did on my way home from FL. But the gauge is dipping down again just above the 9. So I decide to replace the alternator with a new one and a new belt. On my way home from Sears, The gauge diped lower, so I pull over into the local GMC dealer because the transmission is not shifting properly. Turn it off and try to start it, Dead again.

    The batteries look like they are new, the stamps show march of 09... Anybody else ever hear of such an issue?

    Sorry to go on, but I am frustrated.
  2. unplugged

    unplugged Epic Member 5+ Years 1000 Posts

    I had a similar problem. The symptoms kept getting worse and then the alternator failed, which made for easy diagnosis. (The smoke pouring out of the alternator was a dead giveaway)

    Corrosion and poor grounds are the source of a lot of gremlins. Corrosion on the battery terminals can creep under the cable insulation, and engine to chassis grounds can cause fluctuations in power too.

    Just an aside, pull up the carpet and check for water damage. It would be a shame if you got a Katrina car.
  3. The GMC deal is now saying one Battery is Dead, so I am going to have both replaced. Who makes battery cables for these things that don't cost 500 bux the dealer is quoting for Genuine GM parts. He's not saying I need these, but I am in the mood to change these too
  4. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    No one sells decent priced battery cables.
    Find a local welding supply store and buy "OO" welding cable and thimbles, soldier the thimbles on the cables and replace.
    It'll be a lot cheaper than buying the cables, "OO" welding cable runs about $1.75 a foot.
  5. lowriderinms

    lowriderinms Rockstar


    replace your cables. i used 6awg 110v regular wire n used some lugs n handywork to replace mine on my 6.5 3500. alternator n batts r fine, check your wire
  6. Well I it it back this evening and I still think it's off. When it runs well the Volt Meter is just over the middle of 9 & 14. Tonight it's in the hovering at the 9 region again. So my next option is to find a better garage and replace those wires. Does anyone here know the parts number of the OEM spec so I can try to replicate those wires on Monday my next day off?
  7. Saga continues, this Am I decided to take the Suburban to work. Upon starting it, the gauge is above 11 and running good. I am still planning on replacing the 6 wires that connect the battery to the Suburban.

    I've found a ACDelco list of parts and wire lengths, all are Gauge 2
    Part# 2SD87XG 87" Battery to Battery
    Part# 2SX87-1FS 87" Battery to ? Starter I assume
    Part# 2xxx29-1g 29" long Battery to Ground
    Part# 2SD25x 25" long Battery to Ground
    Part# EG18TK Chassis Strap 18" long

    There was another listed 2sx22 22" long
    Last edited: Oct 4, 2009
  8. Jimmiee

    Jimmiee Epic Member 5+ Years 1000 Posts

    Just a quick note about your voltage. Always use a voltmeter rather than the gauge in the dash. The gauge in the dash may be off by several volts. Usually voltage problems are caused by bad ground cables. Like Tim aid get some good HD cables. The factory cables are usually too small.
  9. Then instead of 2 gauge go with what size?
  10. Jimmiee

    Jimmiee Epic Member 5+ Years 1000 Posts

    2 Gauge is good. I missed that when I read your post. Most stock battery cables are 6 or 8 gauge.

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