Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Charging circuit failure

Discussion in 'The Garage' started by rcamacho, Dec 23, 2004.

  1. rcamacho

    rcamacho 1/2 ton status

    Joined:
    Jul 1, 2004
    Posts:
    1,324
    Likes Received:
    0
    Location:
    WA
    I'm running a 3-wire alternator in my '87. The charging system went out on me a few days ago and I'm starting to look into it now. I'm going to check continuity on the fusible link spade wire tomorrow am. Anything obvious I should check? I don't see a voltage regulator in the wiring diagram, should there be one on this vintage truck? Also, any recommendations on replacement alternators should I have to purchase one?
     
  2. rcamacho

    rcamacho 1/2 ton status

    Joined:
    Jul 1, 2004
    Posts:
    1,324
    Likes Received:
    0
    Location:
    WA
    Well, I traced the alternator ignition hot circuit down to the primary heater/AC circuit. There is a short under the dash causing the 25A circuit to blow. I'm going to rewire the alternator activation circuit to another ignition hot circuit temporarily while I make time to take apart the dash to find the short.
     
  3. fatbob

    fatbob 1/2 ton status

    Joined:
    Jul 3, 2003
    Posts:
    420
    Likes Received:
    0
    Location:
    Phoenix, Az
    Your alt. has an internal regulator, so thats probably why you can't find it.
    I'm confused on what you are refering to as the alt. activation circuit.
    There are two small wires that plug into the alt numbered 1 and 2.
    The #1 terminal goes to a wire that has power when the ign. switch is on. There is a resistor in that wire on trucks with a volt meter, and a small light bulb in trucks with idiot lights. If you dont have the right resistance in that circuit, the alt. will not charge intill you rev it up.
    The # 2 terminal go to the battery, or to the positive cable on the starter.
    When you turn on all your electrical loads and it puts a load on the battery, this SENSE wire detects the voltage level at the battery, and tells the alt to put out more. Some people just hook this wire to the output on the alt. and call it good. But the alt. will THINK the battery is fully charged and not put out as much as it could.
    Heres a great link with some good info.
    http://www.madelectrical.com/electrical-tech.shtml
    Good luck
    Bob
     
  4. rcamacho

    rcamacho 1/2 ton status

    Joined:
    Jul 1, 2004
    Posts:
    1,324
    Likes Received:
    0
    Location:
    WA

    #1 is wired to an ignition hot circuit. Unfortunately it's the 25A heat/AC circuit which has a short in the dash area somewhere and is blowing fuses. I'm fixing the short sometime this week and finding another more lightly loaded ignition hot circuit.

    #2 is unfortunately wired directly to the bat terminal on the alt. which then connects to the battery junction via 8 guage or better wire. I'm planning on correcting this as well by installing a mad electrical alternator wiring kit and a real battery junction block (http://www.madelectrical.com/).
     
  5. tunedportk5

    tunedportk5 1/2 ton status

    Joined:
    Jul 13, 2004
    Posts:
    371
    Likes Received:
    0
    Location:
    Union City, CA
    I have some wiring diagrams I could snap a pic if that will help your
     
  6. rcamacho

    rcamacho 1/2 ton status

    Joined:
    Jul 1, 2004
    Posts:
    1,324
    Likes Received:
    0
    Location:
    WA
    Yeah, that would be really helpful. Please post diagrams fo an 87 if you have them.
     

Share This Page