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Alt not charging battery part 2, please help

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by PetaKane, Sep 13, 2002.

  1. PetaKane

    PetaKane 1/2 ton status

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    Today I took it to an alt shop. Everything came back good as far as their testing showed. Put my alt on their machine, the battery on the big ol meter and everything checks out good. The test showed that at 2000 rpms, the alt was putting out 127 amps, but at idle was only putting out 7-10 amps. I've got March underdrive pulleys and the guy at the alt place told me that they were for 'race use only' and I couldn't use them on a daily driver. Maybe true, but I doubt it as I have run the same pulleys on my previous truck. Anyway back to my dilemna, he said that I could have a smaller pulley for the cost of the tests he just ran. Thought it was cool till I wrote the check for $32. Alot of vehicles have different wiring so I'm thinking maybe he just couldn't see if I had made a mistake in the wiring. I guess my main question should be how can I run a new field wire? Since everything is good and it's just not charging at low RPM's, even with the smaller pulley, it's got to be that field wire that tells the alt how much to charge. I think mine may have been tampered with sometime while it was parked with the hood off at the machine shop. Does it come straight off the coil? I just need to run a new wire from the alt, to every necessary component along the way so I can get this thing on the road again without it dying on me. Sorry for the long post, but since that alt guy was no good, this is my last and probably best bet. Any help will be worth a big ol thank you and sigh of relief on me and my checkbook
     
  2. ftn96

    ftn96 1/2 ton status

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    I had the same problem and it was a bad diode or something in the alternator.
     
  3. PetaKane

    PetaKane 1/2 ton status

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    It's a brand new alternator and everything inside the casing was good. I ran a new 'field wire', from the battery charging stud back to the junction block on the firewall. I don't know if that's where the wire is supposed to go but I traced my wiring diagram the best I could. The greenish brownish wire is plugged in to the plug where it belongs. The red wire on the plug is constant 12V, and on my Chev pickup that red wire is just run all of 3" to the charging stud and connected with a ring terminal splice. I tried that on my Blazer and still no 14V charging. Also got an alt from Autozone and hooked it up, still no charge. Hooked up my old Optima battery that is still good, no charge. All of this just so I could be cool and have an MSD ignition control.
     
  4. sosamantx

    sosamantx 1/2 ton status

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    hmmm, it sounds like the alternator isn't the only problem?? i mean, i think your vehicle should be able to run (on the battery) if your alt isn't charging. that is unless you are running your radio, ac, msd, etc., etc., etc. also, when i was working at autozone, we could only test the voltage regulation, and the diodes on the bench. we had to check current output on the vehicle. so, you might want to check it this way? anyway, i have no idea about the field wire.
     
  5. PetaKane

    PetaKane 1/2 ton status

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    I have to go to work now so I'll have all day to think try to come up with something else to try. I'm just gonna run new wires to the alt I think. STATOR wire will be hot with key in the on position right, or is it hot only when the engine is running? And the FIELD wire just runs to the junction block from the charging stud? I just can't figure this crap out anymore. And I used to like this stuff.
     

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