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Replaced alt. still not charging the battery.

Discussion in 'Elite Explorer 911!' started by superedge88, November 2, 2005.

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    1. superedge88

      superedge88 Active Member

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      My battery was not being charged, the other morning I had to jump start it to get it to the mechanic (for a leaky antifreeze issue) The mechanic told me that the alternator was bad. I replaced the alternator, but still no charging at all. I looked through my chiltons manual, but got no where. I started following the + wire that comes from the alternator and goes to the battery. I found a junction box where there is a 175 amp fuse. I tested the fuse and I get no continuity across it (it isn't one of those clear fuses but kind of an ANL style fuse) Of course I found this fuse after I already took the alternator out to go back and have checker test. I did have checker test the newer one and the old one, both are fine, but they would not let me return the new one I had just bought from them last night. So I am unsure if all I have to replace is this 175 amp fuse, or if there is another possibility that I am not thinking of? Since I also have had problems with my antifreeze leak, I haven't been to work in 3 days! I have to get this vehicle operational, I have changed alternators out before, and I have never had this much trouble before.
       
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    3. sn0border88

      sn0border88 Master Apprentice Elite Explorer

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      the wires maybe shot. Check all points with a voltmeter.
       
    4. superedge88

      superedge88 Active Member

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      I'll do continuity and voltage tests throughout both negative and positive wires.
       
    5. budwich

      budwich Well-Known Member

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      check to make sure that you are getting 12v IN on your alternator.... referred to as the "A SIDE". This "turns on" the regulator and causes 12v + to go out on the "Bside". If you aren't getting the 12vin either the fuse is bad or the lead which goes to your start relay (at least in 96) is no good .... ultimately this goes back to your battery.
       
    6. sn0border88

      sn0border88 Master Apprentice Elite Explorer

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    7. Green98XLT

      Green98XLT Active Member

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      Get a voltmeter and first make sure you have a minimum of 12.6volts at the stud on the back of your alternator.

      If you do, then start the Ex and measure voltage at the same stud on the back of the alt. If there is voltage present above 13.2volts then your alt is fine and you have a problem elsewhere. Replace that 175amp maxi-fuse and with your Ex running, check your voltage at the battery. It should be no less than 13.2v.

      You'll then want to verify that you have the same voltage at the junction box as you do at the back of the alt.

      Remember, a fully charged battery must have a minimum of 12.6volts and the alternator should have no less than 13.2volts or you have something wrong.
       
    8. Brett F.

      Brett F. Active Member

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      What's funny is that I sat in the Advance Auto parking lot and changed out 3 alternators before giving up. Took it to a local Mr. Alternator and they couldn't figure it out. Finaly once of the gurues came in and said check the fuse.

      A freaking fuse was keeping the alternator from charging the battery. Change the fuse out. That is probably all it is. I keep spare fuses like crazy now.
       
    9. orange_exploder

      orange_exploder New Member

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      Did you check the battery to make sure it doesnt have a bad cell. I had a chevy citation that use to eat alternators every couple months. I even bought a new battery right after i changed the Alt the first time. After the third alt i said screw it and took the battery back to NAPA and found out that my new battery had a bad cell. Problem solved.
       
    10. superedge88

      superedge88 Active Member

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      I changed out the 175 amp fuse, works like a charm. Thanks guys!
       
    11. jordanphilipster

      jordanphilipster New Member

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      I have a similar problem, but with a non-similar solution.

      The other day, the charging system decided to quit on me. Car runs, but everything is running off the battery. I know this because it dies after a period of time and a voltmeter shows me 12.6 or lower depending on how long the engine has been running or if the lights are on or not. I have to manually charge the battery to get it back up. I pulled the alternator, autozone says its bad. I get a new one thinking, duh, this WILL fix it. No, it didn't, I still have the same problem. I tested all fuses that I think are related (175amp and the 30amp #14) under the hood, still nothing. I get battery voltage at the b+ alternator post, so I know I have continuity. My guess is that I'm not getting the voltage needed on the A side of the alternator. (My understanding is that this voltage is required to "enable" charging from the alternator) Can anybody tell me what the voltages should be on the small wires going to the alternator? I can't find this info anywhere!

      Thanks!
       
    12. dogbis

      dogbis New Member

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      check your solenoid for the starter. even thuogh it starts find can still cause a no charge situation. I have seen this more than once.
       
    13. Cobraguy

      Cobraguy Elite Explorer

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      I have never seen that 175A fuse blown. It would scare me to death to think about what could blow that.
       
    14. JDraper

      JDraper Somewhat Functional Moderator Emeritus

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      I've seen it smoked once or twice. Usually caused by someone working on the vehicle with it running and accidentally shorting the positive terminal on the alternator to ground with a wrench or screwdriver...(been there, done that...d'oh!!)
       
    15. ohe_boy

      ohe_boy Active Member

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      Swapped out bad alternator with a new one. tested out fine. Left it over night, now battery is completely dead. I mean completely dead. (1.5V)

      Any ideas???
       
    16. skidooer

      skidooer New Member

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      I have a 1996 F150 that keep blowing that 175Amp fuse leading to the alternator. When that happens the alternator isn't charging. When i jump the two leads together the alternator starts to charge again. So i replace the fuse, but only to find that it'll last about a month or so, then the same fuse will blow again. I have checked battery voltage and it measures 12.8v when the motor is off, then when i fire up the truck the charge rate is 14.2v. It appears to blow this fuse out when the alternator stops charging. Is it possible that the diodes in the regulator malfunction and then it put a shot of AC thru the fuse taking it out. Nothing else on that truck has a wire heavy enough to take out that fuse other than the alternator putting out AC or am i wrong. Please help.
       
    17. Moto Mel

      Moto Mel New Member

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      Charging?

      In reading all of these posts I see that no one has mentioned cleaning the battery posts and clamps. I realize that it's basic but, I've seen many starting and charging problems cured by cleaning the terminals at the battery.

      Mel
       
    18. skidooer

      skidooer New Member

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      Those items were the first thing a person would check. Oh by the way, i've been a mechanic for 25 years, but didn't run into this much on the F150. I am not a ford mechanic so they have features there, that don't apply to other manufacturers, but the solenoid and the starter draw was checked. As long as the truck is charging there isn't a problem of any kind. It's just when that fuse blows you can check the alternator and it no longer puts out 14.2 volts. It's not putting out anything. However, as soon as i jump those links together that attach to the fuse, it starts charging again. Hence, install another new 175amp fuse and drive away. this could be good for a month or so, then it returns. I have checked wiring from the rear of that truck including accellery plug in (re for trailers), all the way up the chassis, and that includes the wires on top of the fuel tank. Yet, to know avail. This one has me stumped.
       
    19. ranger7ltr

      ranger7ltr Elite Explorer

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      Blown megafuse is usually a short in the alternator...

      When I bought my current Ford Explorer, ther was no voltage to the rear terminal...Checked the megafuse and it was blown...So I pulled the alternator and had it checked and sure enough it had a dead short to ground internally...

      I had a spare alternator from a Ranger v8 conversion so I changed the case to use the Explorer mounting lugs and had it tested...It was charging just fine so I mounted the alternator into the Explorer...Changed the megafuse and it has been happy ever since...Charging voltage is 14-14.5v and all circuits are happy...

      If your alternator is intermittantly charging then blowing the megafuse, I would test the wiring at the alternator to see if it might be touching the case or body somewhere or the diodes/rectifier bridge inside for movement...Make sure the case bolts are tight and it can't shift a little bit...A little movement is all it might take to ground out an internal connection...

      If there was a dead short to blow the fuse, it would still be there after the fuse is blown and not start charging when you connect the terminals...
       
    20. cattleshow

      cattleshow Member

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      I recently found myself in need of a jump as the the battery was dead and I figured it might be the alternator.As it turned out my NEW sears diehard was a die easy.I had it tested and found out it was defective. Glad I didn't jump in and replace the alternator.
      The tech at sears told me they get a lot of bad battery's back. Paid $110.00 and when I brought it back I noticed a little sticker on it that said made in Mexico. So much for Diehard,Americas best battery as there advertisement says.
      Yes ,the alternator regulater must see 12 volt for it to work.
       
    21. jremington59

      jremington59 Elite Explorer

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      I'm not sure if it's been mentioned yet, but there's also a small fuse n the power dist box for the alt in some years.
       
    22. REsuperG

      REsuperG New Member

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      Anyone have a picture of the 175 amp fuse? I spent an hour yesterday looking through all the wires from the battery and alternator, and could not find the damn thing. I even pulled out the fuse box and still nothing.

      My girlfriends car is totally dead. It starts but is running off the battery. I know the battery and alternator are good, as they are brand new and both were bench tested 6 times. I just bought a starter solenoid, and i hope thats the problem.

      I checked ALL of the fuses and none were blown.

      HELP ME FIND THAT 175 AMP FUSE!!!!
       
    23. ranger7ltr

      ranger7ltr Elite Explorer

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      Do you have battery voltage at the back terminal of the alternator?

      If you do, then the megafuse is supplying voltage and is not blown...If you don't have battery voltage there, then assuming your MY Explorer has a megafuse it would be under the small cover on the back side of the power distribution box on the drivers side under the hood next to the master cylinder..

      I will try to find a picture of the megafuse ...

      Look at the last post in this article...#19...It shows a diagram of the megafuse and its location...http://www.explorerforum.com/forums/showthread.php?t=180814&highlight=power+layout
       
      Last edited: November 26, 2009
    24. REsuperG

      REsuperG New Member

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      On the back of the power distribution box, there is a little plastic cover. It slides up, with one cable going to it, but I don't see the fuse there. As far as the diagram in that post, the megafuse, its not there in that location.

      BTW it's a 1996 Explorer 5.0L 2WD
       
    25. cattleshow

      cattleshow Member

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      Drivers side-look to right of battery.Behind fuse box,lift cover-U will see the battery cable and the starter cable. Between the two posts is a FLAT 175 amp lead strip.Check for voltage on each terminal. Its not your a normal plug fuse.
       
    26. REsuperG

      REsuperG New Member

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      Im going to try and take a picture of the bay. Maybe Im blind, but I dont see the battery cables.
       

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