Edmunds Answers



  • ray80 03/25/10 10:15 am PST

    I hate to assume anything, how can you tell its not being charged? Battery light on or meter/guage thing? Is it a case where battery is dead overnight (which might indicate parasitic drain beoyond normal stuff)?

  • alaskanj 03/25/10 12:02 pm PST

    Are you sure you have the wires hooked up correctly? After the install you yourself can test the output of the alternator and you can even measure charging system voltage drop. Which is the amount of resistance you have in your wires and maybe poor connections. You could have corrosion inside your wiring harness that you cant see, but you can measure with a ohm meter. Do you have a volt meter before I or someone explains the procedure of a charging system test?

  • ineedajob 03/25/10 11:44 am PST

    Without knowing abut the Year, Make or Model, here is the obvious stuff. What's the voltage on the battery when the car is at idle? It should be at least 13 volts, more like 13.5 volts (depending on the car). How about when you rev it up to 1500 RPM, what's the voltage? If it's below 13 volts, you either have a bad Alternator, a bad Regulator or you have something draining the battery and you ASSUME it's not getting charged. How do you know it's not charging?

  • miblet 03/25/10 12:18 pm PST

    it is an 84 dodge ram d100, battery is only reading 12.6 both running or off.And i`m using a multi meter to test. I have not tested directly to the alternator yet.What else can i do if the alternator test like it is supposed to? please explain the charging system test I have accsess to all the tools i need

  • ineedajob 03/25/10 12:45 pm PST

    Here's a quick run down on how a car's charging system works:


    In your case, if you have 12.6 volts running, your battery WILL die shortly. With that said, I would check the Alternator (yes, I know you have replaced it, but rebuilt alternators are not that great but you CAN test them easy enough, or your local auto parts store will test it for free), the Regulator (I think on that year it still was on the firewall and external), the cables/wires especially the GROUND wire (the BLACK one). I remember once going through 4 Regulators to get one that worked on my 1973 Dodge. Sorry I can't be more helpful, my old Dodge brain just isn't ani't what it used to be.

    Either the alternator is not putting out or it thinks the battery is full and won't charge. I highly suspect a bad ground or a Regulator. You can run "cheater" cords (wires) from the ground to the Regulator (black side of the battery to the firewall <regulator>) etc, and see if the voltage changes. If it goes to 13.5 volts, you know you have a loose or broken wire somewhere.

    By the way, I would check all the fuses, just to be safe. It ony take 5 mins. Was this working just fine an it up'd and died or were you working on something (electrical)?

    Good luck!

  • miblet 03/25/10 12:56 pm PST

    I just bought a new regulator and I don`t have a ground wire it is grounded by being attached to the firewall.The only wire going to is two field wires.I know the alternator is good because I had it tested before I left the store.

  • bpeebles 03/25/10 10:21 pm PST

    One really needs some electronics skills and troubleshooting skills to isolate and correct the issue you are describing. A charging-system is not all that complicated.
    Lets see what we know thus far;
    *) Battery apears to be NOT charging as witnessed by measuring voltage across battery terminals.
    *) Battery has been replaced multiple times
    *) You have tried multiple alternators, they all seem to not charge the battery

    Logical assumptions;
    *)Problem is NOT the battery
    *)Problem is NOT alternator

    Next logical troubleshooting steps:
    You need an accurate DVM (Digital Volt Meter)

    Engine NOT running
    *)Measure ohms from alternator case to battery negitive.
    (expecting less than 0.3 ohms)
    *)Measure ohms from alternator B+ battery positive
    (expecting less than 0.3 ohms)

    Fix all problems above before moving on...

    Engine Running
    *)Measure voltage from alternator case to battery negitive (headlights on)
    (expecting less than 100mV)
    *)Measure voltage from alternator B+ to battery positive (headlights on)
    (expecting less than 100mV)

    Fix all problems above before moving on...

    If above readings are good... procede to testing the alternator field voltage and regulator.
    *) If you have voltage across field but no alternator B+ output.... alternator is BAD
    *) If you dont have field-voltage, you have isolated the problem to the regulator.

    (I anticipate by this pont, you have isolated the problem and are well on your way to fixing it.)

    Source: Personal experience

  • docj 03/26/10 4:12 pm PST

    Just to toss my 4 cents in(inflation)(used to be 2 cents)

    Dont assume that it grounded ok because its mounted to the firewall.
    Old Dodge/Chrylser products had terrible problems with grounding issues with regulators and electronic ignition modules....

    Try and run a known good ground wire to the regualtor while its mounted to the firewall and see what happens,just for kicks and grins...
    Seen too many ground issues..especially since the Bodys tend to rust out on these....

    Also...is the new regulator painted or just metal looking?
    If its painted,file or grind off the paint on the back side of it before mounting it and clean,file the firewall mounting area as well to ensure a good ground is made...very important...
    must be free of paint,rust ,etc...both surfaces,firewall and regulator

    Good luck

    Doc J

  • alaskanj 03/26/10 5:08 pm PST

    Two things here, 1st one, does the new alternator have a voltage regulator build into it already and you now have two regulators for the same system that are working against each other??? Alternators now a days have the regulator built in... Second some external regulators we're ADJUSTABLE and had a screw for that, could it be yours is set too low and doesnt have the right output??? Just a few more possibilties to throw out there into the electrical FOG!!!

  • ineedajob 03/26/10 7:04 pm PST

    Old Dodge/Chrylser products had terrible problems with grounding issues with regulators and electronic ignition modules....

    I agree (and I rest my case). I can only go by my 73 – 79 Dodge experiences (and they weren’t that good, that is why I drive a Toyota now).


  • wvarao 04/18/10 5:18 pm PST

    when you buy remanufactured parts its not uncommon to purchase faulty parts several times .thats why i purchase new parts only.

  • alaskanj 04/19/10 12:21 pm PST

    Did this ever get resolved? What was the problem and solution?


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