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Alt amp problem

Discussion in 'Chevy Trucks' started by welj31, Nov 6, 2009.

  1. welj31

    welj31 Member
    Messages: 58

    I have a 86 GMC 4x4 350
    with a meyer e47 plow

    Last winter every time i moved the plow the lights would get very dim and rpms would drop (almost kill the motor).
    This year i had the local alt shop build me a new alt ( 60 @ idle and 170 @ ??) well I installed it with new batt and terminals warmed up motor.
    When I start using any power the volt meter starts dipping down-
    The more I use the lower it goes
    When I turn everything off it starts coming back up but takes a few sec to get there.
    Also it never goes to the + side like it use to.
    I dont thing the thing is putting out the right amps. I dont have a clamp on amp tester. Any Ideas on this?? Thanks
    PS I had advanced auto check it before install votes came @ 14 but they could not test amps?
  2. RichG53

    RichG53 PlowSite.com Addict
    Messages: 1,135

    What condition is your battery in ???? How old and amount of AMPS ??? It may not be able to recoup the charge going back into it .... Or the battery is getting to old to handle the drain ...
  3. welj31

    welj31 Member
    Messages: 58

    New 925 batt
    New Alt 170 amp?
  4. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Did you run a new dedicated 2 gage charge wire directly to the battery? How about a 2 gage ground cable from the engine to the battery? Any fresh grounds added between the engine/cab/chassis? If you can't answer yes to all these questions then you certainly can't expect a high output alternator to do it job. A component is only as good as it's weakest link. And when discussing electrics/voltage and most important amperage that would be ANY weak links between them. Even a 300AMP alternator will do no good if the current isn't able to flow through the system.
  5. ServiceOnSite

    ServiceOnSite Senior Member
    Messages: 928

    x2 on B&B. That was probally the problem to begin with.
  6. MickiRig1

    MickiRig1 PlowSite Veteran
    Messages: 3,617

    Keep in mind an alternator only puts out 1/3 of it's output at idle. Most plowing is done at a low RPM. Like they said make sure the wiring and battery or batteries are up to the job. The lights will dim when the pump is run but the volts should stay at 12.6 or higher afterward, staying at the + side of the equation.If the engine is sputtering when you run the pump, you have a pump problem. It's pulling too many amps. Which drops the voltage lower then the engine's computer needs to function.
  7. larold83

    larold83 Senior Member
    Messages: 116

    add a second batt i'm putting another one i this season just for my lights
  8. welded wrenches

    welded wrenches Senior Member
    Messages: 177

    alternator amps...

    hi ya..using a 10 si delco remy alternator factory rated at 78 amps is about the only one .that has a low rpm hi out put amps..& and also run a direct positive wire right from the skrew on terminal at alternator. to positive post on battery.oh oh and go get a deep cycle marine boat battery with the starting option...like for use in a large v8 powerd boat..ya can leave the headlites on for half hour..n still start rite up..and doing so yull most likely see a very little headlite dim when operating plow..if only you add 4 extra heavy ground wires in engine bay...negative battery to frame ..frame to firewall near fusebox area...negative battery to plow pump...engine to frame..engine to firwall..and or also battery ground to radiator support (core support) ..also u may a have hotwire shorted out near the engine truck started...common problem fried inside that metal tube near at the starter....i hope this is of some help info..
  9. mcfly89

    mcfly89 Senior Member
    Messages: 306

    Part of the problem here, is he's talking about an ammeter and not a volt meter.
  10. welj31

    welj31 Member
    Messages: 58

    Well here is what we have done so far. First found a missing bracket from the waterpump to alt. I never noticed it before. So that is fixed. Put on a hi grade new belt. And added a 4ga cable from alt to batt. I hear from 2ga to 6ga so I went with 4ga. Seemed like it got a little better, but still not good. Took the whole truck to shop where they built the alt. Owner pulled alt and installed a smaller pulley. We then tested at idle with nothing on and got 14.35v then with everything on and got 14.02v. Drove back home with everything working good. Next night it was cold. Took out truck started turning on things and noticed belt noise. Now this comes and goes with power load. At idle with everything on vote meter is now dipping again. I set idle up 250rpm's (little better). I wonder if I am just over taxing it.
    1) 2 plow lights with high and low beams on (switchable) or both at once. 40amp?
    2) 4 head lights they are set so low stays on with high beams 40 amp?
    3) Heater blower (seems this is very high draw on high.) 20amp?
    4) Regular running lights 5amps?
    5) flashers and low watt led add ons 2amps?
    What do you think I think maybe 100 amp at idle
    Alt is 170 amp IF amp only puts out 1/3 at idle then yes, but shop said is is built to put out 60 at idle. I just dont know if my guess about the draw is right?
  11. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    What about the engine to battery ground cable? Was it upgraded and checked for good connections? You can add all the alternator you want but unless the ground path is also good it means little. The 4 gage charge wire was good though.

    Is this a sinlge V belt setup? If so that's why it slips the belt as load is applied. A single V belt won't support more than approx 100 amps under load. Any more than that and the belt can't hold it.

    You have all four plow and truck lights on at the same time all the time? Why?
  12. welj31

    welj31 Member
    Messages: 58

    I checked the grounds one 6 gage from batt to alt bracket. I will upgrade this on to 4ga too.
    Update now at idle with everything off if i use the plow the vote meter shows discharge fast. The plow cables look to be OEM but only 6ga. I was told to upgrade these too.
    To 4 ga I guess.
    I can run with only 2 plow lights and flashers/led and running lights. I like to use all lights when 20 miles from pavement. lol Thanks
  13. welj31

    welj31 Member
    Messages: 58

    I go some places the other guys wont go. Well really thats most of my job ones no one else wants
  14. welj31

    welj31 Member
    Messages: 58

    I guess I dont understand the point of a second batt I cant even keep up recharging the one??
  15. ETMegabyte

    ETMegabyte Member
    Messages: 41

    I think the idea of having two batteries is to have more "stored" energy available in addition to your alternator.

    You seem to have a problem mostly when actually operating the plow (up and down I'd assume), but you would only go up and down maybe 10-15 times per job, then drive 20 miles to your next job. Also, having all 4 lights on on the truck as well as the plow frame is not something that would be done on the road, so again you're drawing a ton of power only when you're at the actual job, where you're mostly idling or slightly above idle. I'd assume that you go back to regular low beams on the truck and the plow frame when you're back to the road??

    So the dual batteries keep a bunch of power sitting there waiting to be used, providing a pool of power at a time when you're drawing high and charging low. But when you're done the job, the 20 mile drive to the next job will recharge both batteries en-route, replenishing your "pool" of power for the next job...

    You don't seem to have a problem producing power, you just seem to not be able to produce ENOUGH power at idle to keep all your lights going AND operate the plow. Adding a second battery will give you a reserve of power that's not dependent upon your alternator.

    And the high output alternator you just put in will help towards keeping both batteries fully charged...
    Last edited: Nov 12, 2009
  16. ETMegabyte

    ETMegabyte Member
    Messages: 41

    I just had another thought. What about something like <a href="http://cgi.ebay.com/NEW-SPL-SBT-300-AMP-CAPCELL-BATTERY-CAPACITOR-HYBRID_W0QQitemZ390116843309QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item5ad4c69f2d"> a Capcell 300</a> instead of another battery? If one were to want to make SURE there's enough power, you could even go bigger like <a href="http://www.dealercostcaraudio.com/capcell-800.aspx">the Capcell 800</a>... They're designed for car audio use, but how is it any different than what a plow does?

    Car audio pulls a little bit of power all the time, but subwoofers occasionally need a quick boost of power when a bass note hits, and maintain that power for 4-5 seconds while the note plays out. Without a capacitor, you'll notice the poor kids' cars have dimming headlights when the bass notes hit, but with a capacitor in line, there's no dimming of the headlights. Now, for a higher-power audio system, you'd need a bigger capacitor. Same quick draw, same duration, but more power used. That's specifically what the Capcell was designed for. How is this different than a plow? Plows use almost no power most of the time, but when you go to angle it or lift it, there's a quick significant draw at the beginning (to start up the motor) then there's heavy draw for 4-5 seconds while you're angling it or lifting it. It's unusual to have the plow do any one thing for more than 4-5 seconds without some time in between. To me, this seems a perfect use for an ultra-high power capacitor... A capacitor is a device specifically designed to store large amounts of power, and deliver it very quickly when it's demanded. Much quicker than either a battery or an alternator could ever hope to match.

    Putting something like this under the hood and hooking the plow up to IT will give the high-current needed to get the plow motor going without pulling from the alternator...

    Even the smaller one will store and deliver up to 300 amps for 2 full seconds... The bigger one will provide up to 800 amps for 8 full seconds with no extra draw on the alternator...

    It would also have the added effect of isolating the plow motor from the rest of the truck, which I think would be a huge bonus as well... Your alternator would last longer (no more high immediate draw), your main battery would last longer (less heavy discharges and recharges), your belts would last longer (no squeal when drawing heavily on your alternator), and your truck overall would be happier (no computer, car or otherwise, likes brownouts and voltage spikes). Hell, with a big enough capcell, you wouldn't even dim your headlights when you lift the plow, since ALL the power would be coming from the capcell, which would in turn recharge at a more sedate pace between plow lifts.

    This isn't something you would hook your lights up to, or anything like that. You'd run your lights off the main battery like normal, and hook ONLY the plow to the Capcell... The Capcell is designed for quick bursts of energy, which in my mind is the perfect application for a plow... You wouldn't hook the lights to the capcell, because the capcell isn't designed for high-draw constant power (which is what your high-power alternator and battery combination ARE designed for), it's designed for quick bursts, which is how a plow operates...

    It's thinking outside the box, I know, but it's an option... Maybe even a better option than a second battery... A second battery has been "the" solution for plows in the past because it was the only viable option. Capcells are fairly recent. Until recently, capacitors simply couldn't store enough power to make it a viable option for a plow rig, but now they can...
    Last edited: Nov 12, 2009
  17. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Your main problem is your "custom built" high output alternator. Those so called custom built units generally produce less amps at low speeds than the same comparable stock alternator. It takes a fairly expensive and correctly built alternator to produce at least 100 AMP at idle speeds. Which is what a truck used in these circumstances requires to keep the system charged to capacity.
  18. MickiRig1

    MickiRig1 PlowSite Veteran
    Messages: 3,617

    Leece-neville. Big ambulance alternators. These things are huge! 260 amps they do not give the rating at idle.

  19. welj31

    welj31 Member
    Messages: 58


    Well the snow is here. The problem remains. Now truck has 2 new 1000 CCA Batts.
    Every cable on the thing has been replaced with new 2/4 gauge ones.
    I can run everything on the truck all out at idle and it wont dip into discharge (and thats a lot of power robbing stuff). BUT as soon as I hit the plow button WAM right over to full discharge. Lights still dim but not as much. What the hell? Maybe plow motor going bad?
    Close to $500 into it now and problem still there. May be time for a new truck:cry:
  20. RichG53

    RichG53 PlowSite.com Addict
    Messages: 1,135

    Sounds like the Plow Motor is your problem.....