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Charging System on a '79 K5

Discussion in 'The Garage' started by SkyScraper, Sep 1, 2004.

  1. SkyScraper

    SkyScraper Registered Member

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    Charging System on a \'79 K5

    I had a bearing go out a few weeks ago in my alternator. So I replaced the alternator. Now with my new alternator I can't keep my volts up high enough to run other options... like lights and rsdio, etc... (runs 13 or below, according to volt gauge) The other Alternator never moved, it always stayed 13+ volts. So I thought I had a bad alternator. I took it back and they tested it. Everything was fine. /forums/images/graemlins/eek.gif So I gave up on them and took it to another shop and had them get me the part and I put that one in. Still the same problem. /forums/images/graemlins/mad.gif I have looked over all my wiring between the battery, to the alternator, to the starter, and to the ground wire. And everything looks good. I found one problem and fixed it, but the truck is still doing the same thing. /forums/images/graemlins/mad.gif

    My question is, is there some sort of Voltage regulator like there was on the older cars? This truck does not have a computer in it, so I assume I do, but I can't find it. Does anybody have clue if there is one, where it might be... or do you have another suggestion of what the problem might be altogether?

    Lost and confused on this problem..../forums/images/graemlins/confused.gif

    Thanks,
    Scott
     
  2. ugly_blazer

    ugly_blazer 1/2 ton status

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    Re: Charging System on a \'79 K5

    The voltage regulator is inside the alternator. That's all I know about them.
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: Charging System on a \'79 K5

    Too late, I know, but this is one reason I'd rather rebuild my own alternator rather than buy a remanufactured one.

    13 volts should be plenty to power everything, it almost sounds like a poor ground or something. The wires at the alternator are all tight? Made that mistake, now I need to figure out how to remove the alternator, since the terminal is now moving when I try to loosen it. :P
     
  4. diesel4me

    diesel4me 1 ton status Premium Member

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    Re: Charging System on a \'79 K5

    The factory gauges are often very inaccurate--my 82 Cabalaro only showed 11-12 volts on the factory gauge--I replaced the altenator and some suspicious looking fusible links at the solenoid--same reading,11-12 volts.Then a GM tech friend of mine put his hand on the plastic cover on the dash gauges and pressed firmly--the gauge went up to 14 volts! /forums/images/graemlins/eek.gif He said the printed curcuit board gets oxidized sometimes,or the gauges are just plain innacurate.
    I'd make sure its not the gauge--you say it tested fine (asuuming on a voltmeter test)so maybe nothing is wrong,the gauge is just lying to you!.It should put out 14.5-15.5 volts if its working properly--the regulator is built into the altenator case,cant be adjusted--it uses the red wire on the two prong plug to sense the voltage,if it gets a false reading because of corrosion it might cause it to undercharge,also if one or two of the three diodes go out,it will still charge,but at a reduced rate--this ofen doesnt make the "ALT" light come on,or show up on a voltmeter as low output,because it reduces the amperage,not so much the voltage. /forums/images/graemlins/crazy.gif
     
  5. SkyScraper

    SkyScraper Registered Member

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    Re: Charging System on a \'79 K5

    I have been dealing with te problem for the most part since I last posted this. I was doing some testing on what was pulling my system down.

    1) If I turn the Fog lights on on the bumper the Volt meter doens't move.
    2) If I turn the Lights (3) on the top and the Voltmeter doens't move. /forums/images/graemlins/thumb.gif
    3) If I turn all those off and turn my regular headlights on the volt meter drops. Not a lot but noticeable. /forums/images/graemlins/frown.gif
    4) I turn off the head lights and turn the other 2 sets on then the headlights, that's when I see the voltmeter drop. /forums/images/graemlins/confused.gif

    My headlights (to me) seem to be the problem. At least a large part of it.

    I'm having the Alternator rebuilt to push out 100+ Amps. /forums/images/graemlins/thumb.gif If I still see a problem, it has to be a wiring issue. The first place I think the problem is at is in the steering column.

    The reason I say that is because sometimes (something else I have notice lately) when I start the truck at night (only can tell at night) the dash lights are very dim, but I'm showing the volt meter to be in it's normal low position when those light are on. But other times the Dashboard lights are really bright and the volt meter is not reading the same position. It's higher and when I run my other lights it drops but it's tolerable at that point. But if I make a long drive like that. Then the volt meter starts to taper off even if the engine is running at a high RPM going down the highway. I start to lose my volts once again.

    I'm honestly not sure what the problem is but I have checked the wiring from the Alternator to the starter back to the battery and there is nothing that would seem to be causing an issue.

    Let me get my Alternator back from the shop then I'll post again to let you all know if that fixed the issue or not.

    Thanks for all your replies and help!! /forums/images/graemlins/thumb.gif

    Regards,
    Scott
     
  6. BobK

    BobK 1/2 ton status

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    Re: Charging System on a \'79 K5

    I'm not sure how comfortable you are with electrical diagnosis but my 1st suggestion is to purchase a quality DVM(Digital Volt Meter).
    It's an invaluable tool that you WILL use again.A good one will run you about $50.00 and up.

    With the DVM you can sample voltage reading at various electrical connections and try to help diagnose your problem.

    Take a reading from the output terminal of the alt,note that reading.It should be 13.8-14.2 at idle.

    Second take a reading from your alt gauge.See if the gauge is actually giving you an accurate reading.

    Now,if the voltage sense wire is working correctly,you can turn on all your accessories and the voltage at the back of the alt. should still be the same,maybe dropped slightly but should still be over 13.5V.Increasing rpm to about 1500rpm should get the volts back up to 13.8-14.2V.

    If that checks out the alt and "sense" circuit are working correctly.

    Next you would need to isolate where the excessive draw is.
    With the base reading from the back of the alt take readings from the various high amp circuits.

    Back probe the headlights and check that voltage reading.A drop of more that 1 volt is excessive and will dramaticlly effect the performance of that accessory (especially the headlights).
    If the drop is excessive you have a condition known as "voltage drop"
    Voltage drop occurs with old wiring,corroded connections,spliced wires or when a wire cannot flow an appropriate amount of currant to supply that particular accessory.

    Go to Mad electricals site and do some reading.It's very infromative and easy to understand.
    click HERE for the site.

    Of course we're here if you need help as well.
     
  7. SkyScraper

    SkyScraper Registered Member

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    Re: Charging System on a \'79 K5

    BobK - Thanks for that post!! I will try what you have suggested.. makes sense to me!

    I do have an update for this problem.

    I had my alternator rebuilt to push out 90 amps. Since I have had this Alternator rebuilt it is better but I'm still seeing a significant drop in my volts. I see the most when I turn my headlights on or any other normal electrical item on - Like my wipers. If it was something that I hooked like my lights on top and my lights on the bumper. I don't see a significant drop in volts until normal electrical devices are used. That tells me that the problem might be in my headlights or somewhere in my normal electrical components. But where to look... I don't know where to even start at. /forums/images/graemlins/confused.gif I'm not saying the items I hooked up are not effected because they are just the gauge in the truck doesn't move much, but when I run everything you can watch that meter conitnue to drop into the red and it doesn't stop. The truck has never died because of it... but as winter get here, more electrical items will be used.

    All because of a dang bearing going out in my old alternator - If I ever get this one working I'm going to rebuild it myself next time. /forums/images/graemlins/angryfire.gif - lesson learned the hard way!

    Thanks for any ideas on where to look.

    Regards,
     
  8. diesel4me

    diesel4me 1 ton status Premium Member

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    Re: Charging System on a \'79 K5

    It sounds like you have a short curcuit somewhere--maybe in the headlight wires,or a high resistance due to corroded wires.You might want to pull the fuse block apart by removing the screw in the center of it from the engine side of the firewall--somtimes they get gangrene in there from moisture.Did you try using a test light between the battery + terminal and the cable to check for a drain on the system??--if the test light comes on,something is drawing current from the battery--dont mistake the dome light or clock as a drain--if they are on it will make the test light come on too....good luck..electrical problems are a PITA!. /forums/images/graemlins/crazy.gif
     
  9. ZooMad75

    ZooMad75 1/2 ton status Premium Member GMOTM Winner

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    Re: Charging System on a \'79 K5

    Stock headlight wiring is prone to High voltage drops due to the path the electricity has to make. It runs from the Alt, to the fuseblock into the headlight switch, to the dimmer, back through the firewall to the d/s headlamp and then to the p/s headlamp. On mine I was seeing 12.5 volts at the back of the d/s headlight when the alternator was cranking 14.1 (I do have a 110 amp alt though) Thats with no signs of corrosion or any problems with the wiring itself. I installed a set of Relays based on a Diagram posted by DP_90K5 and now get only a .10 of a volt drop to the lights and they are notcibly brighter. My Volt gauge does not even twitch when I hit the lights.

    Here is a diagram I made up to cover the single headlights used on the 80 and down models. Again, based on what DP_90K5 had posted on a later dual lamp system.

    [​IMG]

    If you don't already have your auxillary lighting set up using relay's I'd convert them to relays too. Basically, the more distance the electricity has to travel, the more resistance is encountered and more current (amps) are needed to overcome that resistance. That means more "work" for the alternator.

    Also as it's been said, make sure your grounds are good and your battery cables are not corroded and tight.
     
  10. 3 on the tree

    3 on the tree 1/2 ton status

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    Re: Charging System on a \'79 K5

    The voltage regulator is what the flat 2 wire plug attaches to. You have to split the case to change it, but it takes longer to remove the alternator than it does to change the regulator. Also, every high output alternator I have ever dealt with actually puts out LESS at idle and low rpm than the stocker!
     
  11. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Re: Charging System on a \'79 K5

    Put a digital voltmeter across your alternator with the engine running if you want a REAL answer to your question.
     
  12. camperspecial

    camperspecial Newbie

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    Re: Charging System on a \'79 K5

    I have never replied to a post before, but I may actually be able to help you here. ALL of my GM vehicals have had similar issues as you described. My lights would dim a little while driving, but mostly when the vehicals were idling. The fix in most of these cases was to clean up the connector on top of the alternator. (Usually a plastic connector with two wires, plugs into the alternator) Once clean, USE DIELECTRIC GREASE on this connection. Problem solved for me. Lights do not dim on my 74 pickup,79 Pontiac, or my 85 Jimmy. Remember the KISS rule and I hope this fixes your issue.
     

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