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Hot Rods Alternator

Discussion in 'The Hokey Ass Message Board' started by LEE CHRISTENSEN, Aug 21, 2019.

    Joined: Nov 24, 2018
    Posts: 29


    I recently added a new electric fan and now wonder if my alternator is large enough. I have a 100 amp alternator, here is a list of components:
    Fan. 18.5 amp
    CD stereo amps unknown
    Have AC ( never use it)
    Electronic ignition
    Digital dash
    Plus all other necessities.
    Do I need a larger alternator?
  2. Nope.... Although you may want to check to see if the alternator wiring is up to the task.
    olscrounger, loudbang and Johnny Gee like this.
  3. fastcar1953
    Joined: Oct 23, 2009
    Posts: 2,551


    find out amp draw on everything and add them up. unsure what all other necessities are? tv, hot tub etc.
    olscrounger, loudbang and Texas Webb like this.
  4. Bandit Billy
    Joined: Sep 16, 2014
    Posts: 7,801

    Bandit Billy

    Do you know how wrong this is on this website? We may do it behind closed doors but we don't draw the attention of the villagers. First comes the torches, then the pitchforks...don't ask how I know!!!!!
    RMR&C, Truck64, bobss396 and 3 others like this.

    Joined: Nov 24, 2018
    Posts: 29


    All new wiring and fuse panel put in with build. Kwik Wire
  6. Take the AC out:D
  7. That doesn't necessarily mean it's adequate...
    trollst likes this.
  8. jimcolwell
    Joined: Oct 4, 2009
    Posts: 474

    from Amarillo

    Joined: Aug 1, 2009
    Posts: 629

    from 94577

    Easiest way would be to monitor system voltage.
    Verify what your nominal running voltage is, check it with a few accessories on(headlights, stereo) If the system is dropping voltage quickly then your alternator may not be keeping up with charging.
    If the voltage is getting below 13V with most items on then you may want to look into your electrical system is in proper order(good solid grounds, clean tight connections, no unnecessary loads, radio/amp has proper capacitor, battery is capable of holding a full charge and is not undersized, along with cables.)
    If everything is sorted proper, add up your total amperage load.
    Alternators will burn up if run at 100%. If you are pushing 80A during normal running, then that 100A alternator is going to be working fairly hard, a larger 140A alternator will run cooler and last longer.
    Try and keep the alternator at only 70% capacity total, and when you total your loads add 50% and size the alternator to that. That will get you pretty close to what your alternators peak Ampacity(rating) should be.
    bobss396 likes this.
  10. You don't say if you are having symptoms that would indicate not enough alternator or substandard wiring. As already mentioned if your voltage is staying above 13 volts with your accessories working you are probably OK. If voltage is dropping off or you are experiencing other symptoms the system needs to be checked out.
  11. Roger O'Dell
    Joined: Jan 21, 2008
    Posts: 1,143

    Roger O'Dell

    As long as I have been doing this I never gave a thought to idle amperage. Not sure of your location, but here in SoCal I BELEIVE it to be very important. Call powermaster in Chicago,get the tech line it’s their business. I found them to be very helpful.
  12. Mr48chev
    Joined: Dec 28, 2007
    Posts: 29,584


    Unless you have a big amp and some big speakers the sound system probably doesn't draw enough power to write home about. The dash probably doesn't draw much either, AC = moot point but here where I live you would be using it or leaving sweat stains on the seat.

    I'd say if it ain't broke don't fix it until it breaks. That simply means that if you are out cruising around town on a cruise night or just doing a lot of driving in slow traffic and the rig acts like the battery is low when you go to start it after a stop it might not be keeping up with the demand.
    firstinsteele likes this.
  13. Fish tank... wet bar...
  14. The Kwik Wire harness itself is probably fine, you have their 21-circuit one? Those are pretty robust. I have their 14-circuit one that comes with a 50 amp maxi-fuse. Probably yours is higher. 100 amps is probably inadequate and no margin for error. I run a 63 amp alternator, the only add on I have is the auxiliary electric fan, which draws 21 amps. With it running, the voltage drops from 14 to about 12.5, so my alternator is on the anemic side.
  15. theboss20
    Joined: Dec 30, 2018
    Posts: 247


    The type of alternator makes a big difference along with the ambient temp where you live. The older style Delco alternator was good at low speed in it's original design but probably not at 100 amps. The best low end 105 amp alternator is a CS130 Delco also performs better when operating in very warm weather where most early Delco units can drop their output by as much as 50%. and yes they make them in Chrome.

    Sent from my iPad using Tapatalk
    Joined: Nov 24, 2018
    Posts: 29


    Well, did a amp test as stated to do, and at idle with everything on I still have a 13.2 reading.
    Thanks for all the posts, and when I have to replace the alternator I'll go to the 140 amp. Just to be on the caution side.
    Thanks Again
  17. theboss20
    Joined: Dec 30, 2018
    Posts: 247


    Higher amp units don't always have a good LOW end output...use caution before you waste your money...

    Sent from my iPad using Tapatalk

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