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What Do You Think Of This Wiring? (alternator, Ignition Switch, Starter)

Discussion in 'Early CJ5 and CJ6 Tech' started by CJ51962, Dec 16, 2017.

  1. Jan 16, 2018
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    I would also put a fusible link between the alternator and battery, and a fusible link between the battery and the dash. Modern practice. Look here at the CJ-5 diagram - http://oljeep.com/gw/76_tsm/Section22.pdf
     
  2. Jan 16, 2018
    CJ51962

    CJ51962 Member

    Seattle
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    I picked up some fusible link after reading MAD Electrical’s website. I wonder why he doesn’t pick up the phone these days...?
     
  3. Jan 16, 2018
    CJ51962

    CJ51962 Member

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    I see the fusible link in the diagram, and have searched the interwebs, but have yet to come up with a positive answer on length of link to install. I did read somewhere (so it must be true) that greater than 9” is too much. So maybe 6” is just right. For ease of inspection I’ll install the links at the starter solenoid.
     
  4. Jan 16, 2018
    CJ51962

    CJ51962 Member

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    I understand the ease of installation aspect, but highly recommend reading this article about 1 wire vs 3 wire. Catalog

    However, I recall the 1 wire is often used for tractors, so you may be on to something.
     
    Last edited: Jan 16, 2018
  5. Jan 16, 2018
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

    Tantallon, Nova...
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    The length is largely immaterial- it's the diameter, or gauge, that's important. A fusible link is simple a a piece of wire of narrower cross section than the wire it's protecting covered with some fireproof insulation. If too much current is flowing it heats up & burns out before something else less replaceable can, something 3 to 4 inches long will be fine.
     
  6. Jan 16, 2018
    CJ51962

    CJ51962 Member

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    Thanks Howard. And am I correct that 4 gage smaller than the main wire should be used? For example: 10 gage wire will need 14 gage link?
     
  7. Jan 16, 2018
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

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    That's what I've heard. Note that you should make sure that the alt wire is sized correctly for it's output & work from there. For example a #10 wire is nominally rated at 40 amps, a 14 is 25 amps rated capacity. These are of course rated capacities, it's the "go up in flames" amperage you're really concerned with here. The 14 won't burn at 30 amps but it will be getting pretty warm. For practical purposes I'd go a size higher on the alt wire than what the charts say is actually required.

    FYI:

    "Conduit"
    Max. amp. Circular Cable size Cable size
    drain mils AWG mm2

    25 4110 14 2.5
    30 6530 12 4
    40 16510 10 16
    50 18380 8 10
    70 26240 6 16
    90 41740 4 25
    120 66360 2 35
    155 105600 0 55

    Now this is derived from the electrical code where wires are run in conduits where code says wire heat buildup should not exceed 75 degrees C- in free air they're good for a bit more but I'd be diss-inclined to stray far from these ratings.

    If rolling your own remember to use adequately sized good quality connectors with dielectric grease or other adequate corrosion protection and use flameproof insulation or sleeving.

    FYI-
     
  8. Jan 16, 2018
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    Last edited: Jan 16, 2018
    Rick Whitson likes this.
  9. Mar 27, 2018
    Jonbbrew

    Jonbbrew Member

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    I have upgraded my old VR system to a 10si and am now hooking it up. A few questions..

    1. Since it is a 63 amp i assume i would have to beef up the wire to 6awg to handle such power correct?

    2. This would only be from the pos post on the alternator to the battery or junction post right?

    Thanks! I hope i am on track. I am ready to fire this thing back up soon!
     
  10. Mar 28, 2018
    Rick Whitson

    Rick Whitson Detroit Area 2024 Sponsor 2022 Sponsor

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    Thanks now I am so confused, I hope someone writes this down so I can look it up again. This is the first I have heard about fusible links, but it makes a lot of sense now that I have seen it in writing. For 10 ga. wire use a 14 ga. fusible link, got it, I think.
     
  11. Mar 28, 2018
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    This is how I wired my '82 J20 to eliminate the ammeter in the dash:

    upload_2018-3-28_8-38-48.png

    This is from the 1976 CJ with a 232 or 258 wiring diagram. Notice that there are two fusible links, one from the alternator to the starter solenoid (fusible link 12A to 10 ga alternator charge wire 12B) and one from the solenoid to the wire that feeds the ignition and lights under the dash (fusible link 12D to 10 ga wire 2C, which goes through the bulkhead connector on the firewall to a big splice under the dash). The fusible links protect the Jeep from accidental grounding of the battery positive. Jeep sends the sense wire right back to the charge wire (12E) and connects the ignition to the field with a resistance wire (78).
     
  12. Mar 28, 2018
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    I am fine with a 10 ga charge wire for a 10SI. That's what Jeep used regardless of which 10SI alternator they supplied. The main issue is how much heat the wire resistance will make at full charging current. The wire is short, and running in free air, so the wire getting warm is not much of an issue. Plus the usual alternator operation is at much lower current than the maximum rating.

    10 ga wire has a resistance of 0.0033 ohms/meter. P = I^2 R so for a meter run it makes 13 watts at 63 amps. Calculating the temperature rise is a lot harder (too many assumptions about heat transfer to make), but 13 watts is not very much when distributed over a meter of wire. If you woirry, increase the size to 8 ga. That will make about 8 watts at 63 amps. 6 ga reduces this further to about 5 watts. So the wire is going to get warm even with 6 ga wire.
     
    Last edited: Mar 28, 2018
  13. Mar 30, 2018
    Jonbbrew

    Jonbbrew Member

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    I've seen it both ways. Is it better to have the #2 spade on the alternator to just loop right back to the alternators pos post, or is there an advantage to have it connect back to a general pos post on fire wall ext from battery?

    Also, can an Amp gauge on the dash be wired between the remote positive post and the key switch or does it have to be between the alternator and the battery?

    Happy Easter!
     
    Last edited: Apr 1, 2018
  14. Apr 1, 2018
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    The alternator sense wire can be run back to the battery to remotely sense the voltage. If done this way, it bypasses any voltage drop between the alternator and the battery. IMO there's not much advantage to when the charge wire goes right back to the battery.

    There are ammeters that use a remote shunt. You could put the shunt in a short path between the battery and alternator and skip the long current path under the dash.
     
  15. Apr 1, 2018
    Jonbbrew

    Jonbbrew Member

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    Thanks. And to clarify further what gauge should the two wires #1 & #2 that come from the alternator be? I’ve seen several ideas. Plus with the larger gauge 12,10, 8 etc seems a little harder to find the corrected paddle size on the disconnect connectors for those larger gauge. Does that mean 12-14 awg is ok?
     
    Last edited: Apr 1, 2018
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