Page 1 of 2 12 LastLast
Results 1 to 20 of 40

Thread: Anybody still living who knows old-school charging systems?

  1. #1
    Tuning Addict blindsquirrel's Avatar
    Join Date
    Apr 2017
    Location
    Meridian MS
    Posts
    7,451

    Anybody still living who knows old-school charging systems?

    8A-14 ChargeCircuit.jpg

    I have a 1980s SBC with a 10SI alternator. Allegedly 63 amps (this may be important). Stock replacement alternators for the application, charge system wiring is stock config. For years now, it's had a thing where you can drive during the day as long as you want and everything is great but drive at night for an hour, shut it off, and it won't restart. Low battery. Letting it cool off doesn't bring it back so it's not a hot starter, battery has to be charged.

    It's had multiple different parts-store alternators on it and multiple different batteries. Wiring is good. No-load charge voltage is higher than it should be: 14.80V. No-load voltage decreases a little as RPM increases. With all the loads this old car has the most I can get out of the alt with a clamp meter is ~38 amps. Under max load output voltage falls off to 13.5ish. Increasing RPM does not increase current output or voltage. It's just as bad cold as it is when hot, there's nothing I can do to get more than 38-39A out of it.

    Voltage drops are fine -
    no load (~12A)
    BAT- to alt case 20mV
    BAT+ to alt output stud 40mV
    full load (38A)
    BAT- to alt case 50mV
    BAT+ to alt output stud 180mV

    Is this just junk parts store alternators and they're all using the cheap innards from the optional 43A units? That's sure what it acts like to me. I can't find any other problems. This is completely academic, I have a new 140A CS144 in the mail to do a conversion. It's just always bugged the piss out of me and I want to know WHY YOU NO WORK RIGHT.

  2. #2
    Tuning Addict
    Join Date
    Jan 2015
    Location
    Franklin, NC / Gainesville, Ga
    Posts
    6,736
    I assume the voltage drops were with full load - I know stupid question. Usually if the alternator is capable of putting out 40A (should do like 120A honestly) and the vehicle isn't drawing more than that (big sound system or something) it's just a junk battery. RV batteries are fairly cheap and have larger capacities, but requires reworking hookups. You should be able to put an amp clamp over the cable after everything is hot with full load and measure the draw?
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
    Remote Tuning Available at gh[email protected]
    Mobile Tuning Available for North Georgia and WNC

  3. #3
    Tuning Addict blindsquirrel's Avatar
    Join Date
    Apr 2017
    Location
    Meridian MS
    Posts
    7,451
    Voltage drops were listed both fully loaded and also no load. Battery is fine, it'll stop and restart just fine as many trips as you want, as long as it's daytime and electrical loads are minimal. No key-off draw. There's no problem with letting it sit for 3 weeks and battery still being able to fire it off first try. Battery is a 3-month-old Group 78 Exide AGM - but it did this same thing with other batteries and other alternators going back 15 years. No radio, no courtesy lamp delay timer, no power folding heated outside mirrors. No A/C or electric fan. The only add-on electrical stuff is the backlighting for mechanical water temp and oil pressure gauges.

    Again, it ONLY has a problem after driving with electrical loads (headlights, blower motor, wipers) on. Like you'd expect if all the loads were exceeding the alternator output and drawing the rest from the battery. Not enough alternator to supply the loads on its own.

  4. #4
    Tuning Addict blindsquirrel's Avatar
    Join Date
    Apr 2017
    Location
    Meridian MS
    Posts
    7,451
    Oh, another data point: Clamp meter on the alt output wire shows 38A with headlights and brake lights and blower motor on. Turn on the wipers too, and clamp meter reads exactly 38A still.

  5. #5
    Tuning Addict
    Join Date
    Jan 2015
    Location
    Franklin, NC / Gainesville, Ga
    Posts
    6,736
    Well it sounds like it's charging - just not putting out and when she's ran right at the border like that it'll start pulling from batt. If it was a bad L circuit it wouldn't charge at all. Seen some cluster bulbs cause issues there. I would honestly install an internally regulated - pretty sure that's what you're actually running anyway which takes the l circuit out of the pic all together anyway - with a much higher output.
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
    Remote Tuning Available at gh[email protected]
    Mobile Tuning Available for North Georgia and WNC

  6. #6
    Tuner in Training
    Join Date
    Jan 2020
    Location
    Tampa Florida Area
    Posts
    27
    BlindSquirrel, maybe I can help you find your nut! The 10SI has an internal voltage regulator which was prone to failure. Your ~12 Volt is the key from your info (it should be 14.5 ish). As the voltage regulator degrades, they usually don't fail but don't charge as well, The 63 Amp output is reduced. What happens is part of the transformer/resistors in the voltage regulator will blow reducing capacity by 1/3 or 2/3 (3 resistor bank). So your 10SI is actually only providing a maximum of 42 amps and the voltage will drop also (E=IR electrical theory) so the 10SI will provide enough during daylight but the headlights will cause too much load and then the load comes from the battery. The battery voltage drops along with the 10SI and poof, engine stops and battery needs charged. You really can't easily rebuild the voltage regulator which is why everyone replaced the 10SI. You could go the route or reducing load by using LED headlights but that is a temporary fix. Get the new, ordered, 10SI and it will resolve your issues, assuming the total load is less than the 63 Amp rating. Another key to the failure is your "another point" data. Since the load increases something in the E=IR must change (you changed the R and I remained 38 so mathematically the E (voltage) must drop. With all loads on, check your voltage and if it is changes based on the loads, then you have your proof. Battery fundamentals require a higher voltage than the normal voltage to charge and if the voltage drops below 13.2 volts (2.2V/cell) then you are just sucking down the battery. Us Old-School, Fred Flintstone Dinosaur mechanics, may still have some use in the is technical world where a Google search doesn't have all the answers.
    Bernie Pella
    [email protected]

  7. #7
    Tuning Addict blindsquirrel's Avatar
    Join Date
    Apr 2017
    Location
    Meridian MS
    Posts
    7,451
    14.8V no load, 13.5V full load.

    All of the stock-replacement 63A 10SI alternators have shown this same behavior, though it's only recently I dug in and took real measurements. This has been an ongoing thing across 3 or 4 different alternators over 15 or more years. Take the alt back to the parts store, they put it on the machine with the idiot lights, the light shows it's charging, they say "works fine, no problem with our alternator!"

    This was originally a 229 V6 car that had been swapped before I got it (in 1995). All the alternators I've put on it were looked up for the same car, but 305 V8. Which is a 63A 10SI. The 43A version was used on some models, but according to the stickers I was given the right 63A ones.

    If the soon-to-arrive 140A CS144 does the same thing I'm parking it out in the street and setting it on fire.

  8. #8
    Tuning Addict blindsquirrel's Avatar
    Join Date
    Apr 2017
    Location
    Meridian MS
    Posts
    7,451
    I just realized I was completely ignoring the fact that this clamp meter will also show... the polarity. So. Checking at the main B+ cable at the battery, this shows the charge current making it into the battery. I don't care about any parts of the system that aren't the way alternator current gets into the battery.

    no loads: +3.61A

    high beams: +2.43A
    high beams plus brake lights: +2.28A
    high beams plus brake lights plus blower: +1.18A
    high beams plus brake lights plus blower plus wipers: -1.94A

  9. #9
    Advanced Tuner
    Join Date
    Dec 2019
    Location
    MS
    Posts
    566
    For the alternator to be showing 38 amps in your original post but the last post its not making sense why you only have 3.6a going to the battery.
    Can you check ground amps from batt to block and block to frame/cab?

  10. #10
    Tuning Addict blindsquirrel's Avatar
    Join Date
    Apr 2017
    Location
    Meridian MS
    Posts
    7,451
    The fuesbox/ignition feeds take power from the starter B+ post, the numbers above are only what's left over going into the battery. The starter post is the junction for main battery, fusebox, & alternator output.

  11. #11
    Tuning Addict blindsquirrel's Avatar
    Join Date
    Apr 2017
    Location
    Meridian MS
    Posts
    7,451
    no loads: +3.61A

    high beams: +2.43A
    high beams plus brake lights: +2.28A
    high beams plus brake lights plus blower: +1.18A
    high beams plus brake lights plus blower plus wipers: -1.94A
    Battery SOC indicates it wants 3.61A; any less than that is either because of voltage drop (it's not voltage drop, I measured, on both GND & +) or because the alt can't put out enough to supply both the combined electrical loads and charge the battery at the same time. The last current reading is really the important one, with all those things on the battery is discharging at almost 2 amps.

  12. #12
    Senior Tuner TheMechanic's Avatar
    Join Date
    Jan 2014
    Location
    SoCal
    Posts
    1,533
    I'm going to go out on a limb and say you may have a bad cell in the battery. Might be discharging the other cells when off. Got any other batteries you can swap in for a test?

  13. #13
    Tuning Addict blindsquirrel's Avatar
    Join Date
    Apr 2017
    Location
    Meridian MS
    Posts
    7,451
    The. Battery. Is. Fine. The battery will still crank and start the engine even if it's been sitting untouched with everything connected for 3 weeks, or longer. It is not a key-off problem. It is not a battery problem.

    It's had 3 or 4 different, new, batteries in it over the years with zero change to this specific issue, that being that driving with loads on will discharge the battery but driving with no loads it'll go forever. The current battery is brand new, the previous one was in my Envoy for years and showed zero issues. I know what a battery with a bad cell looks like and this is not that. The battery discharges with all the loads switched on and engine running and alternator output at its max. The battery is not discharging with less-than-all loads switched on and engine running.

    What I'm asking is, given that voltage drops between alternator and battery are fine, and voltage drop on the sense wire is fine, and the battery is known-good, is there anything else that could cause this other than an alternator that just cannot do the output it's supposed to be rated for? Everything I have found points to that one conclusion.

  14. #14
    Potential Tuner
    Join Date
    Apr 2023
    Posts
    5
    I had something very similar to this on my 65 grand prix a few years ago. BELIEVE IT OR NOT, it was the v-belt. The v-belt was riding too high on the pulley and slipping like crazy under higher rpm and load. Just a thought. I know when I was dealing with this EXACT SAME ISSUE, it was hard to consider that my electrical problem may not be electrical at all......
    Last edited by Quik4g63; 05-28-2023 at 07:58 PM.

  15. #15
    Tuning Addict blindsquirrel's Avatar
    Join Date
    Apr 2017
    Location
    Meridian MS
    Posts
    7,451
    Belt is tight, and you can usually hear the alternator whine change pitch if the belt slips, it's nice and steady. It acts exactly like it's a perfectly healthy 40A alternator with a 63A sticker on it, which I suspect is the only thing that makes sense after all this.

  16. #16
    Advanced Tuner
    Join Date
    Dec 2019
    Location
    MS
    Posts
    566
    Put a 200 amp alternator on that thing haha

  17. #17
    Tuning Addict blindsquirrel's Avatar
    Join Date
    Apr 2017
    Location
    Meridian MS
    Posts
    7,451
    140A will be here Tuesday, yeah.

    Just for giggles and because I have no life I put the most recently removed alternator back on just to see how these measurements change. Guess what? This one will put out 40 whole amps! And no-load voltage is (ready?) 14.90 volts! (yes, that's fourteen point niner zero). But under full load, voltage falls off a cliff to 12.40 and battery is discharging at 2.6 amps.

  18. #18
    Tuning Addict blindsquirrel's Avatar
    Join Date
    Apr 2017
    Location
    Meridian MS
    Posts
    7,451
    FIXED.

    20230530_192113.jpg

    No-load voltage at battery: 14.71
    Full load voltage at battery: 14.68
    Current on alt output wire, full load: 48A
    Current into battery at full load: +6.48A

    Same wiring (it's only temporary... unless it keeps working), same battery, same belt & pulley.

  19. #19
    Tuning Addict
    Join Date
    Jan 2015
    Location
    Franklin, NC / Gainesville, Ga
    Posts
    6,736
    So no roasted marshmallows then? I kinda wanted some smores Interesting how all of these with full load only put out that much unless the "full load" is just full load that the vehicle is capable of putting on it and not actual full load via something like a carbon pile tester? Either way you're good now or at least for a year, which is about all I can get out of the parts store alternators any more...
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
    Remote Tuning Available at gh[email protected]
    Mobile Tuning Available for North Georgia and WNC

  20. #20
    Senior Tuner
    Join Date
    Nov 2006
    Posts
    2,608
    I didn't see this till today.. But I immediately though exciter wire issue.. Have you measured voltage on that wire and there is a decent drop between that and the alternators output?
    Tuner at PCMofnc.com
    Email tuning!!!, Mail order, Dyno tuning, Performance Parts, Electric Fan Kits, 4l80e swap harnesses, 6l80 -> 4l80e conversion harnesses, Installs