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Electrical problems

Discussion in '40- & 55-Series Tech' started by paulj, Sep 22, 2003.

  1. paulj

    paulj

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    Took my '76 FJ 40 to a friends farm last weekend to do a little dove hunting. On my way up there I first noticed the a/c cut out, then the radio started fading out, and the gauges started acting wierd with the ammeter way to the left of center. Next the oil pressure gauge started dropping, but when I checked the oil it was full. When I went to restart the truck it wouldn't turn over so we charged the battery for about 4 hours and I was able to get home and charge it overnight. The battery's about 6 months old and the tester showed only "fair" after all that charging. I was able to drive it around town all weekend, but I'm kind of worried about getting stuck a hundred miles from home.
    I'm pretty unknowledgable about electrical work so I had a guy that I really trust that knows cruisers check it out. He put a tester on it and said that it's not the alternator but that the voltages were some times over and some times under depending on what accessories were running and that I should redo all of the wiring which is what he said last time I had an electrical problem. Basically he wants to take the whole wiring harness and unwrap the tape, and then go through wire by wire to find any frayed wires and replace them. It would give me some peace of mind to fix these problems once and for all but I have some questions I'd like answered first.
    1) I saw the post of 8/27 "Dead Battery" and I think that the previous owner of my truck put in kind of junky aftermarket parts. Would having an added a/c overly tax the alternator and/or voltage regulator, and does having an a/c require a heavy duty parts or at least OEM?
    2) Can you get wiring the same colors and guages as the original wires so that when somebody in the future looks at a wiring diagram they can correlate it to the wires in my truck?
    3) How likely am I to get stuck again if the battery's fully charged and I watch the meter like a hawk? I really want to go on my club's trail ride next weekend, but I'd have to drive out there and back by myself about 150 miles each way.
     
  2. Mike S

    Mike S

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    Any time the electrical starts acting goofy, I suspect an intermittant short somewhere. A voltage drop test across all suspected circuits might tell you something useful for zero dollars. Good place to start. :-\

    Mike S
     
  3. CruisinGA

    CruisinGA

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    I agree with Mike S. Also, If you voltages are not consistent, and the alternator is good, it may be the voltage reg. I had a similar problem, after replacing the brushes in my alternator, replacing my voltage reg, and cleaning up all the grounds I could find, I've been fine ever since.
     
  4. s79bj40

    s79bj40

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    might be the grounds, from the battery to the chassis, batt to body, or most likely the wireing around the fusible links next to the battery. This went on mine a few times from getting too hot, and the battery wont charge, the guages wont work, and I couldn't stop or re-start the engine. Gave it a jiggle and it was right again for a while. Re-wired the links and never had a problem again.
     
  5. paulj

    paulj

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    Thanks to all for your suggestions. Now that you mention it, we did notice a loose connection that we tightened, and may need still more attention. Threre's a male and female plug on the wiring harnes near the alternator that's kind of sloppy. What is that plug for? It's green with about 6 or 7 wires coming into and out of it.
     
  6. Pin_Head

    Pin_Head

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    As Mike S. noted, it is a short, not a loose or bad connection. There are a few other things you can conclude from your description. The short is after the amp meter and ends at the fuse block because you are sinking a lot of current but not blowing fuses. Look at the schematic diagram on the Tech links of this site. The '78 one will do. The possibilities are:
    1) the diodes in the alternator are bad allowing current to pass in the reverse direction.
    2) The short is in the ignition circuit or the wire that goes from the ignition switch to the fuse block.
    3) The short is in the wire from the amp meter to the fuse block.
    4) The fuse block is shorted on the non-fused side.

    If the the amp meter only deflects with the ignition key on, then it is in the wire from the ignition to the fuse block, or you have a much higher amperage than normal fuse in the fuse block. If it deflects in the ACC posiiton, the short is in the wire that goes to the radio fuse.