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Wiring Woes: Working ignition, or semi-charging alternator? Your choice.

Discussion in 'The Garage' started by Logan, Nov 9, 2004.

  1. Logan

    Logan Registered Member

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    It was the best of times, it was the worst of times....

    I bought this '84 Jimmy (Sierra Classic, carb 350, SM465, 4x4) back in 98, and had three years of absolutely trouble-free driving from it. Then I
    bought a house an hour outside of town and had to get a daily driver. The Jimmy went to live up at my dad's place
    and basically sat for three years. Other than replacing a frozen battery, and losing a chunk of floor because of a
    leaky sunroof and that damn factory rubber floor cover, I thought it came out of it okay.

    Now, it keeps blowing a fuse (20A, in the lower middle section of the fusebox, can't tell you exactly what it is
    because there's no writing on it, and I can't find a complete fuse diagram anywhere) whenever I start it.... Which
    is no big deal, unless I want to start it again. With the fuse gone, the starter does nothing, and I get no seatbelt
    or choke lights when I turn the key.

    There were two fixes:
    1) I ghetto'ed it up a bit -- I've wired a house lightswitch into the cab, running from the battery + to the
    distributor power wire. Very classy.
    I've got my dash lights back, and she starts every time.... BUT, the alternator never charges this way. As near as
    I can tell, it's comparing Ignition Voltage to Battery voltage to see if it needs to do anything, and since they're
    both coming from the same source now, it's happy to sit on the high side of 8 volts. No matter what.. After a few
    hours of driving, it doesn't have the juice to start itself again, but a jump will get it going every time. If I turn the
    lightswitch off while the engine is running, the alternator will spike up to 18+ volts, so it is working.

    2) I replaced that 20A fuse with a 25A, and it's working just fine... Kinda. Sometimes the alternator kicks in and
    charges this way, sometimes it doesn't. Is 5 extra amps likely to cook the wire? Heh, if so, it'll be easier to find
    the problem. /forums/images/graemlins/wink.gif



    I'm not even sure what I'm asking, really -- It definitely needs someone to look at the wiring, but in the meantime,
    is there any way to 'trick' the alternator into working without damaging anything? I had a look at that 'one wire'
    alternator conversion, but since I'm not sure what else is powered by that two-prong alternator lead, I don't
    really want to try it. Besides, with nothing telling it what to do, it seems that it'd just be charging full-bore all the
    time.

    I was thinking I could wire a double switch into the cab, that could add/remove resistance to terminal 2 on the
    alternator. That should force it to work when it doesn't want to, but may end up overcharging the battery?

    Here's some good links for anyone else having troubles: That first one is the only place I could find that labelled
    the alternator outputs and gave any idea what they actually do.

    http://mightymo.org/Proj_OneWire.html
    http://hotrodders.com/kb/electrical/articles.html

    Thanks for any ideas!
    -Al.
    /forums/images/graemlins/1zhelp.gif
     
  2. Emmettology 101

    Emmettology 101 3/4 ton status

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    I htink the first thing you need to do is find out what fuse you are blowing(as in what it runs to).... Then from there trace the wiring and see if you have a short or broken wire. Try taking a pic of the fuse block and circle which fuse it is. Then maybe someone can help that has a labeled box. I have one at home in my 82........
     
  3. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    Yep, it sounds like you might have two issues?
    Sounds like the fuse is for the hot from your fusebox to your ignition key-> then down to the starter. or what else did you say was on that circuit? your choke light? so check the wires to that light, and the electric choke wire going out to the engine.. /forums/images/graemlins/wink.gif
    The wire could be chaffed through and shorting to ground now and then blowing your fuse. or even the ignition switch itself?
    A voltmeter can be your best friend.. find the ignition key hot wire and start tracing where it goes.
    The number #1 thing that is going to screw you with electrical is CONNECTIONS CONNECTIONS CONNECTIONS! So check the wire and the connections at the ends.. and especially splices.
    Say that hot wire is shorting to ground all the time but not blowing the bigger 25 amp fuse, you'll have a parasitic draw on the battery all the time. That is when you leave it overnight and it won't start the next morning.. but you said it won't start right after driving it for a while.. so like you said it's probably the alternator not charging..
    After you check your battery cables and make sure they are good, tight connections, and the Wire from the alternator to the Battery...
    Hook up a voltmeter right on the battery terminals.. A good battery should be 12.4 volts or higher. Now start the vechicle and let it run, turn on ALL the electrical accessories- headlights, wipers, heater, radio, etc.. The battery voltage should be a minimum of .5 volts higher than that base voltage before you started the truck. This shows you that the alternator is doing its job of keeping up with all your electrical accessories, and still has a 1/2 volt left over to charge the battery.

    Just throwing out some quick ideas to help with troubleshooting..
    Hope this helps a little.
     
  4. Logan

    Logan Registered Member

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    Oky doke -- Had to wait for the truck to come back home...
    Here's two pics. The 25A fuse that's circled used to be a 20A.

    Pic 1 Pic 2

    Crappy pictures, but it'll give you an idea.

    When it's charging properly, the battery reads just over 12v with the truck off, and about 13.8 with it running with everything turned on. Dash gauge reads just a little over 13.

    When it's not charging, dash gauge reads anywhere from 8v to 11v, and the Voltmeter will drop slowly from 12v, but that's the battery holding up the rest of the system. It'll still run if I unhook the negative battery terminal, but the lights go -really- dim.

    The battery cables were new when I got the truck, and the Battery's only about a month old, but I cleaned all the connections.

    There's all sorts of wires under the dash, but I'm pretty sure that's all stock except for a aux horn button. The previous owner had a bunch of crap hooked up including a brake controller for his horse trailer, but I unhooked and properly removed all of that years ago.

    Anyways, I'm sure the wiring is screwed somewhere, but I won't have time to dig into it for another two weeks. (I'm a long haul trucker) If it craps out on her, the GF will take it in for someone to look at... Damn the expense -- I've taken enough extra days off to play with this.

    So, the only questions I can think of right now are:
    1) If it's supposed to kick out ~13.5 volts all the time, can I run two wires from the battery + side to terminals one and two, and put a resistor on one side to force the thing to work... Without cooking the battery?

    2) What's that fuse for? Does anyone have a complete fuse diagram?

    Thanks for reading! Sorry for writing a novel. /forums/images/graemlins/wink.gif
    -Al. /forums/images/graemlins/1zhelp.gif
     
  5. fatbob

    fatbob 1/2 ton status

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    You need a new Alternator. Never ever unhook the batt. cables with the engine running, /forums/images/graemlins/shocked.gifit can blow some of the diodes in the alt. You might get away with it once or twice
    but it will eventually blow one or two of the diodes and you will start having mysterious charging problems.
    Now on those little wires, one of those go to the battery and senses how low it is, battery low / alt puts out near 100%, battery fully charged/ alt puts out 30%. If you try to cheat and hook up the wire to the alt output it will trick the alternator into thinking the battery is fully charged and it will loaf on ya. [not put out 100%]
    Now a lot of people do it, and I think the one wire alts wire it this way. But to get the most out of your alt, run the wire to battery. The other little wire goes to the idiot light [this is one idiot light we really need].Power goes fron the ignition switch, to the light, then to the alt. When you turn on the ignition switch the light gets power from the battery and turns on. When you start it up, the alt. FEELS the draw on it and turns on. When it turns on it sends power to the light, and when the light gets 12 volts from both sides, the light turns off.
    Now I cant remember how to use all the fancy words like resistance, kelvin lead, etc. Or which little wire is which cause I always forget after I get the job done, but I hope I gave enough info to help ya out. /forums/images/graemlins/peace.gif
    Good luck
    Bob
     
  6. Emmettology 101

    Emmettology 101 3/4 ton status

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    Only help I can offer is at Lunchtime I can try and get to my 82 and see what my fuse block has labeled for that fuse.
     
  7. Logan

    Logan Registered Member

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    This is kicking the crap out of me...
    I checked all my wiring, and it seems that I ended up fixing just about every problem that wasn't related to charging. I've taped and/or wire loomed everything that might have been rubbing. That 20A fuse is no longer blowing, so that's a huge step forward.


    The alternator has been tested, and I eventually set it up to work off the 'one wire' system.
    One Wire Alt Picture
    This works pretty well, but it doesn't always start charging. Turning the truck off and on again usually gets it going, but with this setup, I only get 12.8v at the battery, and 14.2v at the BAT terminal on the alternator. There a MOD to get this work properly, but I'm not interested.

    So, I'm going to run my own wires to everything, but I want to double check first -- There are 100 different webpages with all sorts of conflicting ideas about what hooks up where.

    This is what I've gotten out of hunting:
    Terminal 1: (Field) To any ignition hot source
    Terminal 2: (Sensing) To the junction on the firewall
    BAT: I can probably just leave this the way it came from the factory, since this part seems to work. If I do run another wire, should it go to the junction on the firewall, or to the starter? (but not to the battery itself because this just makes the alternator into a battery charger, without powering anything else directly)

    Not sure what else to do -- I might go ask for another alternator just in case this one is actually flakey.

    Thanks for any help,
    -Al.
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: Wiring Woes: Working ignition, or semi-charging alternator? Your choice

    My understanding of the one wire setup is that it can or does need to hit a certain RPM to start charging. I'm not sure this is true or not. Have you tried kicking the throttle after you start it to see? (didn't read the link, sorry)

    About the 12.8 at the battery...if you increase the load on the charging system, does the voltage at the battery stay constant? It's a "12" volt system, so as long as the battery stays ABOVE 12 volts under all conditions, there really is no problem.

    Obviously, the more voltage to the system, the better the lights and heater will work, for instance, but nothing NEEDS 14 volts. Check your battery output at the fuse panel, I'm sure you'll see something like a .5V drop at the fuses from the battery, as a for instance of how much you lose even when things are working right.
     
  9. Logan

    Logan Registered Member

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    Re: Wiring Woes: Working ignition, or semi-charging alternator? Your choice

    Yeah, I tried driving around and kicking up the RPM to get the alternator to kick in, but no go no matter how high or what lights/accessories are turned on or off. Once it decides it doesn't want to charge, I have to turn the truck off and re-start before it'll charge again.

    If it would always charge the way it's set up now, I'd just leave it alone, no question... Gotta wait until 4 for the truck to get home, and then I can dig into it some more.

    If attaching Terminal #2 to the junction doesn't get it to work, then I'm going to go get another alternator -- There must be something goofy with this one.

    Thanks!
    -Al.
     
  10. Logan

    Logan Registered Member

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    Re: Wiring Woes: Working ignition, or semi-charging alternator? Your choice

    What, is it possible that my idiot light just blew out, and that started all this!? /forums/images/graemlins/mad.gif I've got the dashmount voltmeter, and never even thought I might have the ALT light too.
    Wiring Delco Alternator without Idiot Light

    -Al.
     
  11. fatbob

    fatbob 1/2 ton status

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    Terminal 1: (Field) To any ignition hot source
    Terminal 2: (Sensing) To the junction on the firewall
    WRONG
    Terminal 1 NEEDS resistance in the wire to kick the alt on, not just any ignition hot source. But this resistance can easily be supplied by the Idiot light. Test it out for yourself, just hook up an old turn signal light,or anything you have handy to that ignition hot source, and start it up. Does it kick in right away? Now just take that ignition hot source wire and run it straight to the field terminal like you originally planned. It doesnt take much time I you can use whichever way seems to work best for you.
    Terminal 2 is the SENCING terminal. Kinda selfexplanitory, it needs to SENCE the level the BATT is at [you said 12.8v]
    Since you have it hooked up the one wire way at the output, the alt Sences that the battery is at 14.2v. It does work this way kinda but your not gonna get the best performance out of your alt.Test this out also by hooking it up to the junction like you were planning and drive it a day or two then check your battery level. Now switch the wire to the battery instead of the junction and drive a couple more days and test your battery again. Use the way that keeps the battery at the highest level. Let us know which way works best for you. /forums/images/graemlins/peace.gif
    Good luck
    Bob
     
  12. diesel4me

    diesel4me 1 ton status Premium Member

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    Re: Wiring Woes: Working ignition, or semi-charging alternator? Your choice

    Yup--the current from the ignition switch to the small white or brown wire on the altenator plug goes thru the bulb--the bulb has the correct amount of resistance required to make the altenator charge correctly--if the bulb burn out,the altenator gets no current to "excite" the feilds and make it charge(the altenator cannot generate its own current because it has no magnets in it like a generator--it needs 12V going in so it can "boost" it up to the 14.5 it needs to be to charge a 12V battery.)My 74 had the same issues when the prvious owner put a "custom" aluminum stock car looking dash and gauges in it.Sometimes it would charge,sometimes it wouldnt--sometimes I could get it to charge by racing the engine,and it would "kick in" and start charging--never figured out how it got the voltage to make it kick in and start charging.I found the "printed curcuit" thing behind the dash is also part of the wiring for the idiot light and altenator,and it was just hanging under the dash disconnected--so I ran a new wire with a #194 bulb to the altenator plug that was hot only with the key in the "ON" position--havent had any issues since!--I left the bulb under the hood--no place for it on my "custom" /forums/images/graemlins/rolleyes.gifdash---. /forums/images/graemlins/crazy.gif
     
  13. Logan

    Logan Registered Member

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    Re: Wiring Woes: Working ignition, or semi-charging alternator? Your choice

    Okay, thanks again for the help!

    Do I really have an ALT/CHARGE light along with the stock voltmeter? I've never seen the light come on on the dash, so if it's there, it's burned out... BUT, I do get 14.8V at the white terminal when it decides it wants to charge -- Not something that should happen if there's a burnt out bulb in the circuit.

    Wacky. Ah well, one more thing to try...

    Anyone ever converted one of these puppies to electric? Mine spends so much time on the charger lately, it seems stupid to be filling it up with gas too. /forums/images/graemlins/wink.gif

    Thanks!
    -Al.
     
  14. diesel4me

    diesel4me 1 ton status Premium Member

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    Re: Wiring Woes: Working ignition, or semi-charging alternator? Your choice

    If your truck has a factory voltmeter,it wont have an altenator light on the dash,instead they used a resistance wire in the wiring harness(or a resistor,looks just like the ones in a radio!),I know mine somehow found a way to "excite" itself when I revved it up over 2500 rpm--I saw a big arc inside the altenator when it would kick in--I'm sure it wasnt doing it any good!.
    I've seen websites devoted to making an S-10 pickup an electric vehicle,but no full size trucks!!! Good luck with your wiring problems--I've had my 74 since 1990--and I have had nothing but grief with the wiring harness,thanks to the butcher who "customized" the dash and gauges! /forums/images/graemlins/tongue.gif
     
  15. Logan

    Logan Registered Member

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    Re: Wiring Woes: Working ignition, or semi-charging alternator? Your choice

    <Beating head against wall> The wire between the alternator and the starter must be FUBAR. That's all I can think of. Even though It's not hooked up to the Alt, one end is still hooked up to something, and it's grounding out somewhere.

    Right now, the alternator is set up in 1-wire mode... Terminal 2 goes to BAT, BAT goes to the Battery directly. This is the only way I've been able to get it to charge "sometimes". (Hooking up Terminal one to the stock connector or from a seperate 12v source with a lightbulb in series does nothing.)

    The stock BAT wire is unhooked from the ALT, taped up, and ziptied out of the way. Where does this wire really end up? Haynes diagram shows it goes directly to the Battery, while others show it going down to the starter.

    I had a digital voltmeter, but borrowed a needle model from a friend -- When I start up, volts spike up to 14 for a half second, and then drop back down to Battery voltage. Now that I know it's happening, I notice the dash lights go a little brighter if I start with them already turned on.

    Thanks again,
    /forums/images/graemlins/angryfire.gif /forums/images/graemlins/1zhelp.gif-Al./forums/images/graemlins/1zhelp.gif/forums/images/graemlins/angryfire.gif
     

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