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Battery Light On, Yet Alternator is Charging?

Discussion in 'Stock 1991 - 1994 Explorers' started by Tshark299, June 25, 2009.

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    1. Tshark299

      Tshark299 Active Member

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      Last week it wouldn't start because the starter went, so I replaced that and it was fine for about 3 days. Then developed a weak/no start again so I replaced the battery cables that were way past due, and again it was fine for about 3 days.

      Finally last night it would not start again, tried putting a charger on the battery for a couple hours which helped a little but not enough. I pulled the battery out of my Wrangler so see if that would crank it and sure enough it started strong. Since the parts store was closed and my Jeep is not on the road right now anyway, I decided to leave that battery in it for the time being.

      Problem now is that I noticed halfway through my drive home that my battery light on the dash was on. The alternator is charging though, because the volt gauge gets noticeably higher after starting the engine. Basically it starts and runs fine and normally now, except that the battery light will not shut off.

      The only difference now from the way it was originally is that the Wrangler battery is a bit smaller than the Explorers. I think it's a group 56 vs 65. Could that actually make the light come on though? It doesn't seem like the battery should make a difference.

      Any other ideas??
       
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    3. tbe2002

      tbe2002 Active Member

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      I don't know if I would trust the Gauge in the cluster. You may need to actually go to an auto store and have them test the alt. You can either have them bench test it (if u take it off and bring it to them) or you can have them do a load test on the while system. Every auto store I know does both of these for free.
       
    4. rayford2

      rayford2 New Member

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      Check across your battery with a voltmeter while
      the engine is off. With the engine running you should read 1/2 to 2 volts
      higher than the engine off reading. If it's too low it's probably an open diode
      in the alternator or a bad regulator. If it's too high it's probably a shorted diode or bad regulator. The regulator is integral with the alternator, not separately mounted. Easy fixes if you know what you're doing; if not, get another alternator. The warning light comes on if either high or low charge condition exists...Hope this helps.......Ray S. in PA
       
    5. nitro71

      nitro71 Well-Known Member

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      There's a long.. Post by Chetz? about charging system in the 91-94 forum. He tried everything and it turned out to be a fuse. I'd recomend reading that for a lot of good info.
       
    6. Tshark299

      Tshark299 Active Member

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      Nitro, I think I found that thread you're talking about. Lots of good info in there but his problem was a little different than mine. He was having a low charging problem. If anything my alternator is putting out extra juice.

      I did check that fuse box though and I did have one burned out, but it was a 20A, not a 15. I swapped a good fuse in there and it didn't seem to make a difference for me. Light was still on and the gauge was at the "A" or "L" in "NORMAL". With the engine off it's at about "N" or "O".

      I still don't have exact voltage numbers though... I'll try to get them tomorrow while I'm at work and have access to a good multi-meter.

      Interestingly though, the light went off for a minute on my way to work this morning, then was back on again the next time I looked at it.

      Anyone know what the 20A fuse in position 19 under the hood is for??
       
    7. Tshark299

      Tshark299 Active Member

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      rayford, where is the diode of which you speak? Inside the alternator or elsewhere? There are a couple diodes in the power distribution box under the hood.... wondering of one of those might be it.
       
    8. BrianDye

      BrianDye I'll have another... Elite Explorer

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      If thats a 92 doesnt that seem a little high?
      Maybe im getting the gauges confused....
       
    9. Tshark299

      Tshark299 Active Member

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      It's a '93 but yeah.... that's the problem. My battery light is on and I don't remember the volt gauge normally reading that high. Any ideas??
       
    10. chetzar

      chetzar Active Member

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      It seems like the over charging could be due to a smaller battery. Unless i'm reading this wrong, you said you use a smaller battery from your Jeep in the Explorer. Now with a smaller battery, you would need a higher output to keep the battery charged up enough. Now keep in mind with a smaller battery is going to drain faster, thus making your alt work harder. Honestly, if you have alot of accessories, it might not be able to keep up. I would suggest turning off your stereo, disconnecting any amp power cords, or any other aftermarket power cords. This may sound silly, but it will help you get things back to normal. However it dosent seem like your gauge readings are far off, atleast from mine. W/o the engine on, mine reads between the N & O and with engine on it reads between M & A (at idle, at 2500rpm i get all the way up to the right side of the A).

      Also, having your battery on a charger for a "few hours" wont do much if its drained enough to not have the juice required to start (Anything under like 11.3 volts I think). When i took my battery to get tested it was down to 10.9volts and it took the store an hour and halfish to charge it (and they have a retarded fast charger). From what I read it sounds like there is a very good possibility that your battery is no good. And if your alt is bad, and your battery is old, or your battery is bad and your alt is old, it could be both. Best bet is to get both bench tested to ensure proper functionality, they like to shit on people in pairs.

      Another thing you could check is since you said you had starting issue, your starter solenoid might be bad, since the power runs from the alt to the SS, then from the SS to the batt.
       
    11. rayford2

      rayford2 New Member

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      Diodes

      These diodes are pressed into the alternator frame, usually removed with an arbor press to push them out when necessary. I think there are 6 of them for a 95 Amp. alternator. They are tested with an ohmmeter (set on a low range), when they are disconnected at one end, by measuring the resistance one way, and then reversing your ohmmeter probes to measure them the other way. You'll need a soldering iron to disconnect the diode leads for testing. There should be at least a 10:1 ratio between the readings. The diodes you mentioned have nothing to do with the alternator; one protects your computer against reverse current during start and run, I don't have my EVTM handy to say what the other one is for.
      If you're not familiar with alternator disassembly and reassembly you should probably trade the old one in once you're sure it's faulty.LOL Ray S. inPA
       
    12. rayford2

      rayford2 New Member

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      Batteries

      Now here's a note about batteries. They are selected according to the demands of the vehicle. Since most automotive applications use a 12 volt system, the larger the battery, the more current it can produce. A 95 Amp alternator will only deliver 95 Amps WHEN THE ENTIRE AUTOMOTIVE ELECTRICAL SYSTEM DEMANDS IT. This is highly unlikely and indicates a malfunction EXCEPT DURING START, or there are too many accessories running at the same time. And this includes winches and 110 volt inverters among other things.
      What's my point? If you have a lot of accessories and/or the vehicle is loaded with power using options, then get the largest battery that will fit into your battery tray, and has the same height and terminal post configuration.
      Connecting a 95 Amp 12 volt alternator properly across ANY automotive 12 volt battery will not cause an over voltage condition unless there is something electrically wrong with the alternator. And it won't cause an over current condition unless the battery has defective cells.
      A battery charger does much the same as an alternator except it does so under better charging control parameters. If any 12 volt battery needs 10 Amps for charging, that's what the alt. or battery charger will deliver. If it needs 2 Amps the same holds true.....Hope this helps.....Ray S. in PA
       
    13. scas

      scas Member

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      Having a smaller battery in a pretty much stock vehicle is not going to afftect your system up. I ran a small battery after my posts were smashed in by a brute with a 2x4, and the only thing I could find was a battery from a honda civic. Tiny.. Dosen't even sline up with anything under the hood. Then I drove from my hometown of Chatham, Ont to Edmonton AB with, never had any problems with the starting or charging, even in the crappy weather we drove through
       
    14. Tshark299

      Tshark299 Active Member

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      Yeah, I didn't think the different battery should affect the way it charges. I mean, I was always under the impression that the battery was really for starting the engine, and that the alternator should handle electrical demands from there on out. The truck cranks strong and starts instantly, and runs perfectly fine other than the battery light being on.

      Today I drove to the store, the light was on when I pulled out of the driveway but shut off for the rest of the trip there. I shut it down for the few minutes I was in the store and when I restarted it to come home it was on again, and stayed on the whole time.

      The gauge seemed to be in the same place with the light on or off. It was between "A" and "L" with the light on, solidly on "L" when the light was off this past time.

      I've been reviewing the wiring diagrams for the charging system and have decided that my next step is going to be redoing/cleaning up all the positive battery cable connections, especially the ones on the fender mounted solenoid. I'm thinking that if there's a weak connection there the alternator sensing circuit might be getting a false reading. Plus this problem started happening not only after changing the battery, but after I installed the new battery cables as well. Worth a shot at least.
       
    15. Tshark299

      Tshark299 Active Member

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      That other diode in the fuse box is for the 4-wheel ABS system, I found out. And I agree, I'd just replace the whole alternator before messing with the diodes. I'm hoping it doesn't come to that though, since I've already replaced the starter and battery cables, as well as the rear brakes and clutch slave recently, and am trying not to put more money than is necessary into this thing!
       
    16. Tshark299

      Tshark299 Active Member

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      I also solved this mystery and it's unrelated to my problem. Fuse 19 is for the lighting relays in the back of the truck that are part of the tow package, in case anyone was wondering.
       
    17. rayford2

      rayford2 New Member

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      Let us know how things turned out for you.
      Good Luck...Ray S. in PA
       
    18. scas

      scas Member

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      All the battery is really for, is for starting, and regulating the volt to the rest of the vehicle while your driving. Thats why on some older vehicles you can run without a battery.
       
    19. Tshark299

      Tshark299 Active Member

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      So I redid the connection on the fender solenoid and it seems to have helped. The day before I did it the light seemed to be on half the time I was driving, off the rest of the time. Sometimes it would be off an entire trip, but then would be back on again if I shut off the engine for a few minutes and restarted it.

      I cleaned up all the connections on the solenoid post that the battery, fuse box, fuseable links, etc. all connect to. The light came on for one minute the second time I drove it after that, but otherwise the light has not been on at all. Problem solved as far as I'm concerned. The voltage gauge was always in the same place whether the light was on or off anyway, so I'm not too worried about it.
       
    20. YBCold

      YBCold Well-Known Member

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      i have similar problem. voltage is low at start up and then levels out about 13.5V to 13.6V when i hit the accelerator. also voltage drops at stops and when i change into reverse. or have headlights on and AC on at full power. i had sub woofer and amp but i removed it. and still problem persists. i also took the alternator to autozone and had it checked and it passed. battery is new too but already is down to 11.8 volts. not sure whats wrong. takes about 1 month to completely discharge battery.
       
    21. rayford2

      rayford2 New Member

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      Low volts

      If the vehicle is idling at the proper RPM when in drive, and the alternator is good, then you might have what is called "excessive parasitic drain". There is a certain amount of current flowing when the engine is off to keep the electronics alive. This shouldn't exceed 50 milliamps (.050 amp) with the engine off.

      To test this you need a DC Ammeter (common in multimeters). Set the meter to the highest DC Amps setting and make sure your test leads are connected Black to meter Neg. and Red to meter DC Amps (change to ma when your test goes below 500ma). Disconnect the POSITIVE connector from the battery. Connect the Black test lead to the Battery Pos. post and the Red lead to the disconnected pos. wire. Decrease the meter range until you find a reading that doesn't overload the meter. This reading should not exceed .050 Amps (50 milliamps). If it's over, you'll probably need a EVTM manual and start disconnecting circuits until you find the bug.
       
    22. YBCold

      YBCold Well-Known Member

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      ill attempt this, i think my wiring is bootlegged. although bout a year ago it went to a shop and they said the injector wires were shorted out. im not too sure how to diagnose problems with the injectors though. my drive belt seems ok too.
       
    23. YBCold

      YBCold Well-Known Member

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      ohwell. accidently broke starter relay while bolting B+ back on. and also replaced my negative battery clamp. already charging much better at 13.84V. my voltage still drops a little at redlights and goes really low in reverse. should i be concerned?
       
    24. rayford2

      rayford2 New Member

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      While it's true you can run a lot of vehicles from the alternator alone, it's not really advisable to do so for a long period of time.
      Yes, the battery provides the power to start a vehicle, but it also performs another function a lot of people don't realize. The battery also provides a constant source of power since it is also a storage device of electricity. It works much the same on power as your vacuum reservoir canister does for your vacuum system.
      So, while the vehicle is running and the battery is connected it provides a constant source of power irregardless of what switches on or off during driving.AND it relieves the alternator from these spikes that occur when accessories go on and off.
      The BATTERY actually runs the vehicle when connected and the ALTERNATOR leisurely keeps adding juice to the battery when it's turning.
      The alternator has to work much harder without the battery.
       
    25. Tshark299

      Tshark299 Active Member

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      Just a quick followup to my original problem... the light has still not turned on once since the day I cleaned up the connections on the solenoid post that branches out to everything else. So my problem is solved as far as I'm concerned!
       
    26. rayford2

      rayford2 New Member

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      That's what it's all about...getting the problem solved. Thanks for letting us know the outcome. Solutions are just as important as advice...Ray S.
       

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