Can’t get an alternator to put out a charge

Electrical & Ignition

  1. saylor

    saylor Senior Member

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    i found that dl7552 alt just by type/size 130a and the pulleys look like they have a chance.

    upon sleeping on the issue, i think i just am going to see if i can make my ALT spin faster. i know its rigged up the belt path is not stock, as i deleted the A/C compressor (and therefore its pulley).

    i have a 4 groove crank pulley. 1st one is WP. 2nd one is P/S. 3&4 are ALT/AC dual-belts.
    deleting the A/C compressor forced me to change the belt routing.
    I shimmed out the ALT mount forwards a belt width so its now aligned with pulley #2 and #3.
    i left #1 belt path stock.
    #2 belt path now runs P/S and ALT, with a 61" belt.
    #3 and #4 are empty.

    how have other people routed their belts after deleting A/C compressor?
    Im looking at adding an idler pulley where the A/C compressor used to sit, or flipping the ALT upside down and running it underslung, or something.

    i have a non A/C water pump pulley here but i dont think it lines up with the A/C crankshaft pulleys to do ALT/WP like on a non A/C car..
     
  2. 78Brougham

    78Brougham Deplorable FCBO Gold Member

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    It's not a matter of spinning... it's output. You can spin that fucker a million rpm... if it's rated at 60 amps that's all you're gonna get no matter how fast it spins. :rofl:
    You're drawing way too much from the battery and that little fucker can't keep up.
    You need 130 A to run all your gear and that wasn't including headlights, probably a huge group 72 deep cycle marine battery wouldn't hurt either.
     
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  3. saylor

    saylor Senior Member

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    ok - whats an alternator output curve then?

    how come if im going at highway speed, it CAN keep up?

    when does an alternator 'kick on' and start to produce voltage/amperage? 0001 r.p.m?
    no, close to 1000-1200r.p.m from what I see in all the charts. and its a curve, its not full on or full off all or nothing.

    so I am tending to disagree with spin !=output. I think if, at idle, I can make the ALT spin faster, I can get it to generate enough current such that it wont draw on the BATT. not to say there is not a top end - I think it can reach a max and then that's it you hit max output.

    good discussion I appreciate it.
     
  4. detmatt

    detmatt Old Man with a Hat FCBO Gold Member

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    I’d think you’re best bet it to get the alternator that best suits your needs so you’re not continually replacing insufficient ones. How often do you want to be left stranded, do it right once, if something is worth doing it’s worth doing right, etc..
     
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  5. stubs300

    stubs300 Senior Member

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    Sometimes that's to complicated for some people to understand!
     
  6. traintech55

    traintech55 Senior Member FCBO Gold Member

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    Exactly Stubbs, Automotive electricity, is very simple, yet only 45 % of people working on cars understand it. You have to have higher amps, to operate all the new fangled accessories out there.
     
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  7. 78Brougham

    78Brougham Deplorable FCBO Gold Member

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    Almost every one of my cars at idle puts out at minimum 14 volts at idle. My MGB and Elite both need a boot in the ass, as in a blip of the throttle, to get it to go but after that they're fine till I shut 'em off. Lucas... LOL
    My '67 Imperial will start to flutter a bit after a long light with all the lights on, but the tail lights are a huge draw, but no big deal.

    I'm thinking you'd better heed some advice that's been given here and pony up for the proper output alt.
    I'm out.
     
  8. Gerald Morris

    Gerald Morris Well-Known Member

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    Your alternator is keeping up the voltage at full spin because despite the nominal ratings of your devices, they seldom actually draw their full load. Some times they do though. THAT is when having a high current alternator behooves you. Your battery will supply current to your loads and recharge when it can. In the long run, overloading the ampacity of your alternator and wiring will cost you more dearly than investing in the proper alternator and wiring to start with. Expect shorter life for both your present battery and alternator.

    You will do well to wire that charging lead in #2 AWG for now, even with just a 60A stock alternator.

    I don't recommend that DL7552 AT ALL. Its a CHEVY alternator for one thing, and will put you through more minor bullshit than any cost savings you might accrue. Don't be "penny wise and pound foolish" here.

    Get one of those Tuff Stuff rigs. I plan to. I COULD rebuild one of my squarebacks w a heavy duty stator and diodes, but why show off my tech savvy and blow any chance at a warranty? Its not worth it. Even impoverished as I am, Commercial Off The Shelf (COTS) is the best paradigm.

    I pray it works out for you.
     
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  9. furious70

    furious70 Active Member

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    I have an older gm 1 wire on mine, it's ok but I'd use the newer denso with AR engineering mounts.
    Different alts have different charging curves, modern ones put out a ton at idle. Old school 100a ones can't do it at idle, they trade idle amps for peak amps, that's just what 50yr old tech was capable of.
     
  10. saylor

    saylor Senior Member

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    THIS! THIS is the discussion we need to have around here. good, spirited ones, with lots of opinion and experience and observation!

    from what im learning on the interwebs, ALTS can be driven anywhere from 1:1 to 4:1 ratio, depending on pulley setups. most kick on/start to produce voltage at around 1100r.p.m ALTERNATOR SPEED not car idle speed.
    maths:
    Ratio = Crankshaft Pulley Diameter / Alternator Pulley Diameter
    You can then determine the rotor speed using your known ratio:
    Rotor RPM = Pulley Ratio x Engine Speed (example; 2.1 x 870 = 1827 Rotor RPM)

    powermaster recommends 3:1 on street car, without any more details about the application, thats a safe answer and covers most everything. until you get into +6000 ENGINE r.p.m 3:1 = 18000 alternator r.p.m.s. then the alternator thinks about coming apart.

    DL7552 alt comes up as chry 5th ave so i dunno where you saw it on a chebby. i also found a slantsixdan post where he says thats the most direct, cheapest way to get more juice on an old chrysler. he further said get the 50/120 amp - 50at idle, 120 anytime else.

    i am looking at powermaster and tuff stuff alternators also. i have emails out to both sales depts asking for specs. we will compare them to the DL7552 off the vatozone shelf and see what we see. i got to have big voltage at idle speed or the whole experiment is getting me nowhere. im never gonna hit 6k r.p.m. so i need a better pulley ratio or an alternator that puts out better at very low speed.


    Your Pal -

    - Saylor
     
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  11. saylor

    saylor Senior Member

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    aigh so I ordered a 50/120a alternator. I should have the time to try it this weekend. this is the one slantsixdan posted would be the most direct-route upgrade. additionally, on jalopyjournal, I found where a guy put one of a 440 and he said it all lined up. stay tuned.
     
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  12. 78Brougham

    78Brougham Deplorable FCBO Gold Member

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    Nice work! Just don't change the crank diameter. That will affect your power steering pump speed and your water pump speeds. Those may overspeed as well.
     
  13. saylor

    saylor Senior Member

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    no, see, thats the whole deal this whole time i said it a bunch for months and no one could reply. i deleted the A/C compressor (therefore pulley) and had to change the belt routing. Ive asked about it here and got crickets.
    First my car was overheating, so I changed the waterpump belt routing back to stock. but i had to kick the alternator up to crank POS#2 (#3&4 orig)and is now connected to P/S pump same belt.

    i tried calculating the driven gear of 6" with a 5" pulley and a 2" pulley on a single 61" belt to calculate r.p.m., and the math is beyond my skill level.

    so, THERE is the need to spin my stock ALT faster. its running at some unknown rpm with this setup currently.
     
  14. twostick

    twostick Senior Member

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    If the crank pulley diameter didn't change then deleting or adding the A/C pulley will have zero effect on alternator speed. Crank pulley dictates the belt speed and the alternator pulley size dictates how many RPM the alternator spins relative to belt speed.

    Kevin
     
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  15. saylor

    saylor Senior Member

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    it all changed. i had to walk the ALT forwards on the crankshaft from the last 2 grooves forward to crank #3. Then removing the A/C pulley of size X, and introducing the P/S pulley of size Y, thats not even supposed to be on the same belt path. am i really the first guy that ever deleted A/C compressor? i figured someone surely has done this before me.
     
  16. saylor

    saylor Senior Member

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    @Big_John if thats you on jalopyjournal - please extend my thanks to pzookey for his posts about the 7552 alternator. slantsixdan wrote about them, then i found pzookeys posts with a pic even of it mounted to a 440.
    i ordered one today and should be goofin with it this weekend.
     
  17. traintech55

    traintech55 Senior Member FCBO Gold Member

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    When most people remove the A/C compressor they convert the brackets and crank / water pump pulleys to that of the non A/C cars. Then you can still run the double pulley alternator and use the inside groove.
     
  18. saylor

    saylor Senior Member

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    traintech55 sir! does the front crank pulley ass'y just bolt on / off? i have a non A/C 383 sitting here. i could unbolt the crank pulley and swap onto a 440?

    the crankshaft pulleys are for sure different between A/C and non-A/C at least on the 2 motors i have.

    i'd hate to do all that work, but damn.
     
  19. traintech55

    traintech55 Senior Member FCBO Gold Member

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    If both your engines are pre 1972 the crank pulleys will interchange. Remember ONE of the six crank pulley bolts is offset, you will have to align all six holes. The water pump pulley will go right on. Your alt belt will then drive the water pump and alternator, the power steering uses its own small belt. In fact if you have a non A/C engine with all the brackets, all B/RB engines use the same.
     
    Last edited: Dec 18, 2019
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  20. saylor

    saylor Senior Member

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    rgr rgr thanks yes i do i have a complete non A/C 383 and a complete A/C 440 here both 1968.

    thats just a damn bit of work. but good to know i appreciate it. i may have to go there.