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Need help - High output alternator question

Discussion in 'Chevy Trucks' started by CASMEDIC, Dec 16, 2004.


    CASMEDIC Junior Member
    Messages: 15

    I've got a 2003 Silverado 1500 Z71 with a Fisher 7.5' that came stock with the 105 amp alternator. I replaced it with a 160 amp alternator. The manufacturer of the new alternator says I need to upgrade the alternator wire to a 4 gauge cable. The stock wire is an 8 gauge fusible link. Will I be safe just changing it to a 4 gauge cable or must I keep a fuse in there - and if I have to have a fuse, what size/rating? Please let me know - I'm tired of trying to find the answer to the question. Thanks-

    -CASMEDIC :drinkup:
  2. Tarkus

    Tarkus PlowSite.com Addict
    Messages: 1,113

    The fuseable link may fail. Your 105 would have cut it fine given a chance. You could have gotten by with a 120 amp with stock wiring and fuse too. The fusable link saves you if there is a major short circuit in charging buss. You will need to upgrade link or do with out it. You could also make one by splicing a short 3 inches or so piece of 8 gauge wire alt ouput lead too so it will burn off before 4 ga smokes. Make sure "fuse" is in a area it can "burn" without taking out other wires. You could pig tail it right off alt with 8 ga and then splice 4 ga to it. Also make sure the rest of the circut can handle the extra current. What I do with dual batteries is run a second charge wire for alt to second battery (usually 8 ga with a "fuse") so the some of the charge current load is taking off of the rest of the buss.

    CASMEDIC Junior Member
    Messages: 15

    The plow alone isn't the reason I upgraded my alternator. I plowed for the last 2 winters with the stock alternator - no problems. I added some extra electrical stuff this year and I needed more juice-
  4. Tarkus

    Tarkus PlowSite.com Addict
    Messages: 1,113

    You can run a lot of stuff on a 105 amp alt as I do in a few trucks and never had a dead battery yet or even close to it. I do use dual batteries though.
  5. PackRat

    PackRat Member
    from Kansas
    Messages: 47

    If the manufacturer recommends a 4ga, then by all means, run a 4ga. DO put some kind of fuse, breaker, or fusible link inline. May keep your rig from going up in flames.

    Bear in mind, fellas, that alternators are designed to maintain a fully charged system. Alternators will not recover an electrical system, like a generator. These late model alternators are not designed, and will not support, recovery of a system. The salvation of an alternator on a plow rig, is that you do not have a constant heavy draw on the system.
    I'm seeing the same thing, on our company Pete's. They are factory 140amp Delco, and will fry like eggs, if you try and recover a discharged system, while running all the lights.

    Dual batteries will greatly help an alternator, given the high discharge capacity, when properly charged. Our Pete's run 3, or 4, 950cca units, and work great, until someone lets it run down. Then, down goes the alternator, and here's a bill for a $500 road call.
  6. Tarkus

    Tarkus PlowSite.com Addict
    Messages: 1,113

    In a pinch 6ga will work fine if you cannot find 4 ga as it will take well over 200amps to fry it. Also 2ea 8 ga have the same load capacity as one 4ga and 2ea 10ga the same as one 6 ga and so one if you want to route smaller wire in loom. You are not compromising anything with using the two light wires as that is how the wire sizes tables were laid out to begin with load capacity wise.
  7. Frozen001

    Frozen001 Senior Member
    from Rome NY
    Messages: 908

    I would no recommend this type of "Fuse". First off wire is not meant to act like a fuse. Second if I were to use wire as a fuse it would have to be solid wire, not stranded wire, which in the larger gages is $$. Third if the "fuse" were to burn up and break the connection, you will now have an exposed wire since there will be nothing around the burnt up wire to insulate it from its surroundings(like a real fuse). Go to a local car audio dealer and buy one of those large fuses that they have for high output stereo amplifiers(I have seen them up to 250 amps). They are not that bad $$ considering the piece of mind (The fuse holder will be the most expensive part).

    Again I would not recommend this. I am sure that the wire sizes will be close when comparing a single wire to two smaller wires, but I can think of issues that might cause one wire to fail, giving you only one wire to carry the load. For example suppose the connection point on one fail due to corrosion(which is common in snow plow trucks, as well as any vehicle that sees winter weather).

    One more thing. Just because a wire is rated at 200 amps, does not mean that you should draw 200 amps through it. As wire carries more current the wire temperature will rise. Then with the rising temperatures, the wire will begin the get soft and will sag, the internal resistance of the wire will increase, causing the wire to heat up more (though not much), and last the outer insulation of the wire could begin to melt which could cause a short if used in this state for an extended period of time.
  8. Tarkus

    Tarkus PlowSite.com Addict
    Messages: 1,113

    You obviously do not have much of a understanding of electrical curcuits and wire rating as your comments show. You ALWAYS use a small multi strainded wire (the more the better with fine strands the best) for a fuseable link as it will burn off cleaner and quicker than a solid one will as the strands start to break down and that is the whole purpose of it. It will take a bit over 200 amps to burn off a 10 ga fuseable link quickly. A 8 ga one will take closer to 300 amps to pop. Fuseable links are not designed or rated like fuses.

    You could follow this guys advise above though and have your truck possible catch fire when there is a short circuit. With 4 ga wire use a 8 or 10 gauge multi stranded fuse link of about 3 inches or so with high temp insulation on it and make sure it is in free air no touching anything because it will run warm normally. (do not use regular plastic insulation on this "fuse" as it may melt in normal use) If you use 6 ga feed use a 10 ga fuse. Also you do not what pure copper wire for fuse either. Copper clad conductors or even a specail steel alloy wire are best for this.
  9. Frozen001

    Frozen001 Senior Member
    from Rome NY
    Messages: 908

    I do not see you logic... I under stand stranded wire will carry more current, and that at the wire breaks down it will be cleaner(i.e. the smaller strands will begin to burn up therefore a cascade effect will occur buring up the strands), but ANY FUSE I have seen is always a solid piece if wire, and fusable links ALWAYS have extra insulation around the fusable area to prevent the broken lead inside from being shorted. Any to me a wire that is running WARM is a bad thing, and not NORMAL. Why not just do it correctly and get a large fuse and use the properly rated wire gage. Cobbling something together "in a pinch" is not the correct way to do things. Homemade fusable links are not the way to go in my opinion, too many thing could go wrong (wrong length wire, improper gage selection, wrong insulation).

    CASMEDIC Junior Member
    Messages: 15

    Problem Solved

    I thank you all for your input. I solved my 'problem' last week. I was finally able to find a 175 amp fuse (believe it or not at AutoZone). I ran a 4 ga wire to the fuse, then 4 ga to the battery. Worked like a charm. We had a snow storm yesterday and everything worked perfectly. I just need to shorten the wire a little bit more to make it fit a little better in the engine compartment - other than that, it's perfect. Thanks-

  11. Frozen001

    Frozen001 Senior Member
    from Rome NY
    Messages: 908

    Congrats on doing the install CORRECTLY instead of throwing something together that "sort of" works. I am sure it will give you no problems at all.
  12. Brad3000

    Brad3000 Junior Member
    Messages: 2

    High Output Alternator... Fusable Link?

    Read through this thread with much interest as I installing a 235A Alt on my H2 (OEM is 130A iirc) to handle a decent amount of accessories including 2-way, winch, and GPS gear. I am at the same place CASMEDIC was at and wonder about installing the manufacturers 4guage replacement cable for the 8guage OEM fusable link that came with the car. I am also installing an dual battery system using Odyssey PC-1200's but haven't decided yet to go with the 2 www.hellroaring.com isolation switch configs vs a simple solinoid switch...

    I have killed 2 ACDelco batteries already in 2 years and I need some serious battery juice replenishment, hence the new 235A alt.

    I wonder if anyone can suggest a source for 200A fusable link (4guage?) with the appropriate insulation instead of installed a fuse link a T-series to handle the load..?

  13. shooter

    shooter Junior Member
    Messages: 13

    IMO if you are going to run high amp draw acc, upgrade both the positive side(alt to batt, batt to distribution block) and the neg side as well (neg post of the battery to the frame)
    Dont leave the factory wire to handle the neg side of the truck.
    Also check with your local welding supply house, 4 gauge fine stranded wire for welders carries more amps than normal wire.

    Last edited: Apr 10, 2005
  14. Brad3000

    Brad3000 Junior Member
    Messages: 2

    Thanks Shooter.
    I learnt a long time ago that marine stores often have better qual gear than automotive ones. I have 1/0 guage wiring for an aux battery & internal 2Kw ProSine invertor in the car and it has a T-series 400A breaker on that feed. This aux system is not connected to the car "grid". The westmarine store near me knows me by 1st name ;-) as I always use stainless components where poss, even replacing bolts that show rust etc. Their heavy-guage wire is pretty good for auto use...

    For the fusable link off the alternator (called generator in the serv manual?) I have been searching for and found the Littelfuse Mega 200A & holder. I haven't figured out yet what amps I should cover - with a slow blow or fast blow 200-250A. The tested OP of this alt is 233A @ 5000rpm but H2's 6.0L Vortec engine rarely gets over 3500rpm which translates into 204A...


    Regs Brad.
  15. calhoun

    calhoun Senior Member
    Messages: 165

    When I installed a 2500 watt inverter I just went to napa and got a fusable link holder and then installed a 200 amp fuse. This also can be used as a shut off by just removing the fuse, if needed. 4 gauge seems real thin, I installed 00 welding cable to carry that much power. Needed to upgrade the ground wire also.
  16. GetMore

    GetMore Senior Member
    Messages: 179

    Brad, was that rpm rating at the alternator or the engine? The alternator is turned faster than the engine, as a matter of fact I think it is close to a 3:1 ratio.