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Thread: Fluctuating voltage problem

  1. #1
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Fluctuating voltage problem

    My volt gauge in my 89 Lancer Shelby jumps around. I’ve confirmed it is not the gauge with a meter. I ve tried multipe alts multiple power boards, and adding a large ground wire.

    How should I go about doing more thorough tests? I haven’t tried a. Different logic board.

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    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: Fluctuating voltage problem

    Try a different logic board. It's the piece that measures the voltage and tells the power board to adjust the field coil in the alternator. Check both power board and logic board grounds.

    I'm intimately aware of the signals and connections of the two boards right now doing my SMEC rewire. Lol.

    Brian

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

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    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Fluctuating voltage problem

    I did a little thinking today and tested the voltage with the car off. The voltage will fluctuate with the turn signal, key forward, engine off. To me that indicates that I have a problem with my power side from the battery since my grounds all look pretty darn good. I'm going to do some testing at the battery terminal today and see where that takes me.

    If that doesn't turn up, I'll make a cal and put in a new logic board. I don't think I have another 069 board that's stock.

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    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Fluctuating voltage problem

    This is very frustrating. I now have a better looking battery terminal setup than I've ever had before, and the voltage still fluctates.

    My battery is one of the red top optimas which I purchased off of Amazon a while back. Could the battery be faulty internally, and somehow causing this problem? I'm getting pretty stumped. I have an extra 8ga ground, and all the connections on the positive terminal look great to me.

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    Supporting Member Turbo Mopar Contributor
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    Re: Fluctuating voltage problem

    How much does it vary? Does it change much you increase the load?
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

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    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Fluctuating voltage problem

    It can swing by about 3-4 volts. If I step on the brakes, or use my turn signal the voltage spikes. Sometimes it'll spike up to almost 18 volts on the gauge, and other times there's not much difference at all. That's when I'm driving. With the engine off, I'm seeing a direct correlation between the turn signal bulb lighting up and the voltage dropping about 2 volts or so.

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    Supporting Member Turbo Mopar Contributor
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    Re: Fluctuating voltage problem

    A voltage drop of 2 volts with a simple turn signal sounds like a bit over the top to me. I checked my Sundance with a two month old 1000 cranking amps battery moments ago, Yes I love big batteries, I cannot lie.....
    Anyway I get a voltage drop of 0.02V which is 100X lower than yours. What is your not running current from the battery to the car? I can measure mine if that would be helpful to you. LMK
    How about disconnecting your battery and run jumper cables to your other car with to the battery terminals of the Lancer? Now repeat your experiment.
    I just finished with a bizarre battery issue, the battery would test with a 100amp load at 400 cranking amp. At times it would not start the car but the issue was not the car side as it acted similar with the CSX and the CSX battery worked without flaw in the Sundance. I even swapped the questioning battery back into the Sundance for another test. Same result. So out it went....
    New battery no problem
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

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    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Fluctuating voltage problem

    The jumper cable idea is fantastic. Thanks for that one. I'll do some more testing tonight. I was getting some weird readings on my meter last evening, so I'll change out the batteries and give it another go.

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    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Fluctuating voltage problem

    OK, while my meter is still giving some funky readings (ohms will flash between O.L and 0.000 only when testing between battery posts) I did a lot of testing and determined that everything wiring wise was good, and the new terminals I'm using are likewise in good shape. When I put the battery out of Joy's Daytona in the car it fired up with more vigor than it had in a long, long time and the voltage was rock solid while hitting the brakes. There is enough of a voltage drop to dip the gauge slightly with the turn signal still, but nothing much to speak of.

    Honestly, with the way the car started, I now realize that the battery was on its way out since last fall when I thought the cable was bad along with perhaps the terminals. I think I'll take the battery in to get tested now and report back with that.

  10. #10
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Fluctuating voltage problem

    The battery tested good, but it's clear by the way that the Walmart special fires the car up that it was bad.

    Does anyone have a suggestion for batteries these days? I'm assuming that Optima won't pay out on the warranty for a battery which tests good.

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    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: Fluctuating voltage problem

    Quote Originally Posted by cordes View Post
    The battery tested good, but it's clear by the way that the Walmart special fires the car up that it was bad.

    Does anyone have a suggestion for batteries these days? I'm assuming that Optima won't pay out on the warranty for a battery which tests good.
    walmart everstart higher end battery (the maxx or whatnot.... not the valu crap one) made by johnson controls which is a good battery.

    walmart batteries used to be exide.... exide are sonsabitches. seriously, they are scoundrels.

    Brian

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

  12. #12
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Fluctuating voltage problem

    That's actually the battery which was used to conduct the test and determine that the original one was bad. I'll pick one up. Thanks for the suggestion.

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    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: Fluctuating voltage problem

    since i know you are a frugal man, i also suggest finding a local interstate battery and calling and asking for a "blem" or a blemished battery in our battery size. (group 34 for a SL according to rock auto though i think i run a group 26 in my reliant.... i have a group 34 in my 07 T&C van though....interstate didnt have a g34 blem so i have a everstart maxx) should also be a johnson controls battery and will be significantly cheaper. my buddy called a year ago and got one for 48$ because the printing on the battery was buggered up. not the construction, but the label lol.

    Brian

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

  14. #14
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Fluctuating voltage problem

    Now, we're talking! Thanks for that tip.

  15. #15
    turbo addict
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    Re: Fluctuating voltage problem

    when looking for a battery on the real cheep look to see if you have any small battery remanufacturers locally too

    they can be dirt cheep though nothing beats new brand name on the blem rate lol

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    Supporting Member Turbo Mopar Contributor jonnymopar's Avatar
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    Re: Fluctuating voltage problem

    I've always had excellent luck with NAPA batteries, but they certainly don't give them away. I had a beyond-cheap Sears battery in my Neon for a while and it would crank no problem in any weather, but you could see the headlights almost "pulsating" at night sometimes randomly. I put in a NAPA Power battery and everything is rock solid now, even with a 212k-mile alternator.
    Jon J.

    1989 Daytona ES 2.4L DOHC
    2003 Neon SXT - gone but never forgotten

    If it ain't broke, fix it 'till it is!

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    Moderator Turbo Mopar Staff Force Fed Mopar's Avatar
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    Re: Fluctuating voltage problem

    Oreilly Super Start batteries are made by East Penn, and work good. And they have up to a 3 year warranty. I have a Super Start Platinum agm-type Group 35 in my Daytona, and it's a beast.
    Rob M.
    '89 Turbo GTC

    2.5 TIII stroker, 568 w/ OBX and 3.77 FD

  18. #18
    Garrett booster
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    Re: Fluctuating voltage problem

    Do you know how to do a voltage drop test? If so I would do one. It's quick and easy.

    When you do it to your battery end go directly from battery post because this will also test the connection between post and clamp.

    The drop test will identify high resistance faults in your cables, posts and connections and confirm or rule it out.

    Beats throwing money at a problem.


    I saw you mentioned putting your meter on your battery posts on ohms mode. Why?


    EDIT: Found this. Do this with everything you can possibly turn on to put as much load as possible on the system during the test.

    http://fme-cat.com/docs/1519.pdf



    Looking at cables and ends doesn't confirm 100% that it's electronically sound. Many times I have found serious faults at or near cable ends in which the cable looks flawless but the fault was exposed by testing and repairing it fixed all the issues.

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    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Fluctuating voltage problem

    Thanks for the tips. I have not done a voltage drop test prior to this. I'll give it a go to see where I'm at, although things appear to be quite sound after the battery swap.

    The reason I was putting the meter on the battery terminals in ohm mode is because I knew that those should read OL. Something is amiss with my meter, and I'm thinking of finally sucking it up and buying a real one. The one I have is decent and comes recommended from the internet when it comes to the budget type meters. This one was only about $40. I'm at a loss as to why it'll oscillate between OL and 0.000 ohms when on that supposedly good battery which is giving me the trouble. I guess it could be an internal fault that's causing the issue?

  20. #20
    Garrett booster
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    Re: Fluctuating voltage problem

    Actually putting your VOM on your battery posts in Ohm mode should not read OL. It would probably read closer to zero ohms. I can't think of a single reason or instance I have ever put my meter on a battery in anything other than volt mode.

    If you want to test a meter / leads simply short the leads together in ohm mode. Should read 0 or damned close to 0. If not your leads or meter are messed up. That test pretty much only tests your leads.

    If your old battery passed a load test and now after installing a new battery your symptoms are gone or mostly gone I don't think the battery had anything to do with it.

    I would suspect 1 of 3 possibilities.

    1. Your battery connections were bad and by installing a new battery you temporarily fixed it.

    2. One or more than one of the cables going to your battery are flaking out and by messing with them installing a new battery it temporarily fixed it.

    3. The 14 pin connector on your SMEC is flaking out. Your alternator connects to that. When they flake out it can cause your charging system to do all kinds of odd things. Installing the new battery may have temporarily made the connections touch properly again at that plug to the SMEC.

    I had issues with that style connector on my LM / PM car. The car would literally die if you touched that plug and the alternator would stop charging at times. It was all traced down to the female pins weren't tight enough. Bending them a tad bit solved the problem.

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