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burning out alternators?

Discussion in 'General Explorations!!' started by choppc, January 1, 2004.

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    1. choppc

      choppc New Member

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      I'm helping a friend out with her 1997 explorer. It was in the shop to have a heater core replaced last week. She got the explorer back tuesday night of this week and the truck made the 10 minute drive from the shop to her place w/o any problems. Howevere, the next morning it wouldn't start - dead battery. Having to make a drive of about 5 hours, she simply borrowed a charged battery of the same capacity at hers. On the drive, the truck died again and needed to be jump started.

      I ended up pulling out the alternator on the road-side and we went to a Pep Boys store and had it tested, with the results indicating a defective alternator. A re-mfg'd one was purchased and I installed it. We then used jumper cables to to a bit of a charge on her battery before starting out on the road again. About 35 minutes later, the truck died again and a voltmeter showed that the battery voltage was down to about 6.5 volts. Finally, we had it towed the remainder of the trip.

      Now, I pulled the battery and the new alternator and had them both tested at a parts store. The battery turned out to have a bad cell in it and the new alternator still was outputting 14.7 volts. The original battery was also tested and passed the test but was in need of being recharged. I recharged the original battery and then re-installed the new alternator. The problem still persisted and the battery ran down again.

      They Haynes diagnostic manual for this vehicle indicates that there should be 12 volts on the B+ terminal when the key is in the "off" position. There should be 12 volts on the B+ and A terminals with 1.0 volts on the I terminal when the key is in the "on" position with the engined stopped. There should be 14 to 15 volts on the B+ and A terminals and 14.0 to 14.7 volts on the I terminal with the key in the "on" position and the engine running.

      I tested the alternator and with the engine running I was getting 12 volts [dropping at about .1 volts every couple of seconds] on the B+ and A terminals and 0 volts on the I terminal. I took the alternator back to a local Pep Boys store and exchanged it for another re-mfg'd one and installed it.

      Re-testing with the engine running immediately after installation of the 2nd replacement alternator resulted in getting all of the proper voltages on the B+, A and I terminals. However, within 2 to 3 minutes of starting the engine a low beeping noise sounded from within the dashboard. This was not the "ding ding ding" sound that indicates that the key is in the ignition switch when the door is open, etc... This was just a low sounding series of identical beeps. I immediately re-tested the voltages on the alternator terminals and once again had 12 volts on the B+ & A terminals and 0 volts on the I terminal.

      Additional checking out of the vehicle shows that the gas gauge is not working, the battery/alternator light won't come on at all and the rear window wiper is not working.

      At this point I think that the mechanic failed to properly reconnect all of the wiring connectors in the dashboard when he was done re-assembling the vehicle after replacing the heater core.

      I'm also trying to determine is if there is anything else that he could have done wrong that would cause the alternator to fail. It might just be bad luck that I managed to get 2 defective alternators from Pep Boys but I don't know if it is reasonable to consider that.

      I have also considered that perhaps something in the circuit that controls the voltage regular switch on the alternator might be damaged such that it never tells the alternator to swtich on and produce a current to charge the battery. I understand that the B+ terminal is always hot [the fuse link is OK - I tested it] and is the heavy gauge wire through which current flows while charging the battery & providing power to run the vehicle when the engine is running. What I'd like to know about the A and I terminals is if there is some procedure that I can perform to bypass the external circuitry to "trick" the alternator into operating if it is in fact a problem under the dash that is simply telling the alternator not to operate properly. Is there such a procedure? Do I just need to apply a connection to the +12 volts battery terminal for both the A and I terminals to do this?

      Please advise. I'm not sure how many times Pep Boys will let me exchange the alternator. I also need to be armed with enough technical information to make sure that the mechanic isn't being deceitful w/respect to what he may have done wrong while working on the vehicle.
       
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    3. Rhett

      Rhett Let Them Eat Cake

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      Are the belt and belt tensioner working the way they should?

      Are all the fuses ok?

      The shop where you had the heater core work done should take responsibility for their work if they're reputable at all.
       
    4. Billy177

      Billy177 Well-Known Member

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      i forget when this was fixed but i know that there is a direct relation to the charge light in the dash and the alternator people will argue otherwies but i think that replacing the lightbulb may be your prolblem
       
    5. choppc

      choppc New Member

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      Yes, the serptine belt and the belt tensioner are working properly. I've checked all of the fuses, both in the access panel in the dashboard and in the engine compartment, as well as the fusible links [including maxi fuses] and they are all OK.
       
    6. Opera House

      Opera House Well-Known Member

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      Yes, the alternator is turned on by the idiot light. There is a resistor across the bulb in the event of a bulb failure. I would check to see if the battery light comes on when the key is just turned to on. If not, it is likely a connector under the dash has a bad connection because it is not fully inserted.
       
    7. choppc

      choppc New Member

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      OK, I'm just gonna ask you to repeat that again to make sure what I'm understanding is what you intended to say.....

      You mean to say that if the bulb battery/alternator light [located in the instrument cluster] burns out then the alternator itself will either fail or will remain in a switched "off" state while the engine is running?

      This is on a 1997 explorer, 5.0 litre V8 engine, 130 amp alternator.
       
    8. choppc

      choppc New Member

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      No, the battery light does not come on when the key is turned to the "on" position with the engine stopped.

      OK, if the idiot light controls the alternator being switched on then my thoughts are leaning towards it being a loose connector but I won't rule out a burned out bulb. Given that there are other gauges & controls not working properly after the heater core was replaced I'm thinking the mechanic either did a sloppy job or he broke something.
       
    9. ld50

      ld50 Oh, the money you`ll blow

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      :eek: I`ve never heard about the idiot light controlling the alternator, I am skeptical, but I thought my truck only had front anti-lock brakes for a while..hmmm...
      You guys are sure huh?
       
    10. ld50

      ld50 Oh, the money you`ll blow

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      :D

      Well I`ll be hornswaggled, you might have something there. I found this info on GM systems, sounds like what you were saying. Learn something new every day, but wouldn`t it be wise to mention this in the shop manual?
      (or does it somewhere?)

      http://www.misterfixit.com/idotlite.htm
       
    11. Opera House

      Opera House Well-Known Member

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      Other dash problems point directly to the installation. Other posters have reported dash problems when they have either replaced the heater or done dash work. As an electronics designer, turning it on by the lamp circuit is a beautiful way to reduce wire count. As I said before, there is a 510 ohm resistor paralled to the bulb in the unlikely event it burns out.

      All you have to do now is convince the nechanic that it is his fault. As a temporary measure you could go to Radio Shack and pick up a 470 ohm 1/2W resistor, connect that to the LG/R wire at the alternator plug and connect the other end to some fuse that has switched power. A single strand of wire would easily fit into the fuse socket. That would get you charging again.
       
    12. choppc

      choppc New Member

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      OK, just making sure here, LG/R is the "light green w/red stripe" wire, as opposed to the yellow wire, on the 2 wire connector that attaches to the alternator, right? Per the diagrams in the service manual, this is the "I" terminal.

      I have some 470 ohm 1/2 W resistors in my electronics hobby supplies, so it wouldn't be a problem to implement that particular work-around to the problem if it becomes necessary. I will just have to determine which circuit is appropriate to tap into for this purpose.

      The mechanic did pay to have the vehicle towed to his shop and is now working on the problem [free of charge]. I'm just hoping to get him to reimburse for the alternator & towing expenses that were incurred as a result of his mistakes.
       

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