Voltage issue(99' Ram 2500)

Discussion in 'Hangar Talk' started by Matthew K, Nov 10, 2017.

  1. Matthew K

    Matthew K Line Up and Wait

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    Hello all,

    so as some of you may know/remember, I drive a 99' Ram 2500 with the 5.9l cummins. I've noticed something "interesting" within the past few days. I'll be driving along at 60mph and I'll look over and see the voltmeter is at 12ish volts. This happened once the other day, and went away after 2 minutes or so and then again today. Today I was making a U-turn and noticed it, accelerated and it stayed there, pulled off after a minute, shut off the engine, started it, and after a few seconds it went to 14 volts. Changing RPM doesn't appear to change anything when this is occurring, but the reaction time on the stock volt meter is slow so the rpm could be making it increase slightly. I have verified this voltage as I have a ham radio installed that tells me the voltage when I first turn it on.

    The first time this happened I thought the alternator had just died on me, but since it still appears to charge after these events occur, I can't imagine the alternator is to blame as once they die out their usually not going to come back(although I'd prefer this since replacing an alternator would be pretty easy). The only thing I can see causing a large drain on the alternator is the grid heater coming on, but since this has occurred at 60mph, the heater should DEFINITELY not be on at that speed, since it is supposed to shut off when you are over 20mph. Also, I'd expect a noticeable power difference if the heater was on at that speed, but it has run just like normal during these occurrences.

    Could this be the voltage regulator going out? Or somehow the grid heater? I'll be sure to double check, but I'm pretty sure it isn't any wiring shorting out.
     
  2. Zeldman

    Zeldman Final Approach

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    Do easy stuff first. Hook a volt meter up to the battery and start the engine, then see what ya got.
     
  3. Matthew K

    Matthew K Line Up and Wait

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    The voltage is good when this event isn't occurring, I'd like to hookup my amp meter to the alternator and also the grid heater and see what I get, but its a waiting game as to when it happens again.
     
  4. Zeldman

    Zeldman Final Approach

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    Ahhhhh...... gremlins..... good luck.
     
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  5. mondtster

    mondtster Pattern Altitude

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    Unless the logic for the grid heater changed considerably between the slightly older trucks and the '99, they won't be turned on at highway speeds. But it is the season you'd start expecting them to cycle so it is reasonable to think that is a possibility.

    Assuming that the grid heaters are not running, I'd start suspecting the alternator. If it is the original alternator it is getting pretty old and the brushes may be worn and intermittently making electrical contact. The voltage regulator on these trucks is in the ECU and it seems rare for them to go bad.
     
  6. Matthew K

    Matthew K Line Up and Wait

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    Ah, so it is possible for it to intermittently work/not work? I've always read/heard that once it stops charging, its not coming back. But your reasoning does make sense. I'm not sure if the alt is original, but the truck has 247,000 miles on it, so if it is, the alt has had a good life. I am going to check tomorrow though and make sure there isn't any corrosion on any of the contacts. If not, I am leaning toward it being the alternator.
     
  7. mondtster

    mondtster Pattern Altitude

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    Yes, an alternator can occasionally get intermittent. Checking all connections is a good start. If you want to eliminate the grid heaters from being a possibility, disconnect them and drive the truck for a while to see if the volt meter returns to normal. They draw 200 amps so when they are active you will definitely see the voltage droop because the alternator can't keep up.
     
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  8. Matthew K

    Matthew K Line Up and Wait

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    @mondtster @Zeldman Just cruising the local autoparts stores right now, but are there any major differences between a "Nippondenso" & a "Bosch" reman alternator? I'd go for the Bosch immediately, but it is an extra $110(almost double the price), so I was wondering if the Bosch is significantly better enough to justify getting it? Same amperage output.
     
  9. Omalley1537

    Omalley1537 Pre-takeoff checklist

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    I’m not sure if the 99 is the same, but the later ones (03-07) were semi-notorious for the crossover cable (between the two batteries) corroding and losing connection and/or becoming intermittent. Sometimes the break was under the insulation so both ends would look fine. This also applies to the other heavy gauge cables in the system. Might be worth some basic continuity testing before jumping into parts replacement.
     
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  10. Matthew K

    Matthew K Line Up and Wait

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    Thanks, I'll make sure to check that.
     
  11. mondtster

    mondtster Pattern Altitude

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    I believe ND was the original manufacturer so you're likely getting the same alternator either way, Bosch is just a branded rebuild shop and it's hard to say what the other shop is that did the cheaper one. I personally favor taking your alternator to a local rebuild shop rather than taking whatever the auto parts store has in stock to sell you.
     
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  12. Zeldman

    Zeldman Final Approach

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    I prefer to have the one I have rebuilt. Unfortunately the most excellent electrical motor rebuilder in my area passed away a few years ago. I used to rebuild my own alternators, generators and starters years ago, I just might try my hand at doing that again.
     
  13. gkainz

    gkainz Final Approach PoA Supporter

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    on my prior Ram CTD ('97), the voltage regulator was built into the PCM. My PCM went south and I had that issue while on the road. Bought an external Chrysler voltage regulator (for an old vehicle) and hooked into the system which allowed me to get home and source a rebuilt/replacement PCM. I might be able to chase down the details in my old files, if you think it may help.
     
  14. Matthew K

    Matthew K Line Up and Wait

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    Well I checked the wiring, and there was some surprise(within the past 2 weeks) corrosion on both of the batteries. Not a huge amount, but enough. I'll be cleaning them to eliminate that as a problem and see if the problem occurs again. If it does, I'll probably go ahead and get a new alternator, its old enough that a new one wouldn't be wasting anything.

    @gkainz At this point I'm not thinking that's the problem. I'll keep it in mind though.