Possible alternator problem ?

Discussion in 'Shop Talk' started by AstralBear, Dec 18, 2004.

  1. AstralBear

    AstralBear Active Member

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    I have a rebuilt alternator in my truck that isn't charging the battery . I got a new battery , changed the regulator and it still doesn't charge the battery ( all the time ) even though the alternator test out OK when put on a tester in the parts store . I suspect it's an intermittent problem with the alternator as it charges sometimes but not all the time.

    Anyone know about this stuff?
     
  2. Beeman

    Beeman Well-Known Member

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    OK, we're guessing at the type of truck. Chrysler/Dodge trucks have problems with wires breaking in the harness causing your problem. You say it has a regulator so I'm ASSuming it's an older truck. You can full field or test the alt. on the truck by jumping the wires at the reg. which will also test the integrity of the harness. If we know what vehicle we can give details on how to do this.
     

  3. AstralBear

    AstralBear Active Member

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    A 1989 ford F-150 4.9 liter engine , straight 6
     
  4. moopups

    moopups In Remembrance

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    A quick and reliable field test for an alternator is to place a long screwdriver down near the center of the back and front of it. There will be a magnetic field at both places of a correctly working unit. Beware the cooling fan when doing this because the engine needs to be running.
     
  5. HermitJohn

    HermitJohn Well-Known Member

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    If the alternator and regulator test out on machine at auto parts store, then it has to be a wiring problem. Find a manual with wiring diagram and get a VOM and track it down, unless you see something corroded or disconnected (check where harness plugs into alternator and regulator for corrosion). Been too long since I messed with a Ford alternator with separate regulator to remember how its wired. When alternator on anything I own goes bad anymore, I make an adapter mounting bracket and replace it with a '70s era GM alternator with built in regulator. They are fairly robust and about cheapest alternator around and you can get one at any parts store anywhere in the USA without special ordering anything or getting surprise sticker shock. Also easy to hot wire if necessary and bypass vehicles wiring. You can do same with Ford alternator, but with external regulator, you need to know where everything goes.

    By way if you dont have one built in, install an aftermarket voltmeter gauge somewhere on your dash so you know charge all time. It should show around 14 volt when fully charged and engine running. I like to have both a voltmeter and an ammeter installed, but all ammeter dash gauges I see are cheapo and designed for antique automotive electrical systems and cant handle modern electrical systems since all current other than starter has to pass through them. I am sure somewhere out there is a heavy duty ammeter gauge, but it probably also has a super heavy duty price tag.

    Oh, I dont know what Ford did in '89 trucks, but some alternators on cars (before they went to surpentine belt with spring tensioner) were mounted in rubber bushings and they had to have a ground wire going from alternator case to frame since the rubber isolated them from the engine. Foreign cars especially did this for some reason. Older alternators just bolted to metal bracket and grounded through engine. Anyway this ground wire can break and thus no charge.
     
  6. Beeman

    Beeman Well-Known Member

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    You said it wasn't charging the battery. Does this mean the battery went dead? Are you measuring the voltage with a seperate gauge or are you going by the gauge in the truck(does it have a voltage gauge in the dash?). Fords are known for bad dash gauges in late 80's to early 90's.
    Now if what you have is a condition where the voltage going to the battery is low with the truck running try this. Measure the battery voltage with the truck off. Now start the truck and measure the voltage at the battery terminals. with the truck running at an engine speed of approx 1500 you should get 14v but no more than 2.5 volts more than original batt voltage with the truck off. If your voltage is low try a jumper wire to ground at the base of the regulator and the case of the alt. If voltage is still low unplug the regulator with the truck running and jumper terminals A to F with a jumper wire and watch the voltage at the battery, if it is up to spec now the problem is in your reg. If you suspect an intermittent problem run the truck with the voltmeter attached and shake and tug on all of the related wiring harness and watch the meter.
     
  7. AstralBear

    AstralBear Active Member

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    I'm going to do that test tomarrow . I suspect the problem is an electrical short inside the alternator itself but I'll check the harnesses on both regulator and alternator again with a voltagemeter . It seems like simple wiring to follow and not much could be wrong with the truck wiring ?But I thought maybe there was something I was over looking ?
     
  8. AstralBear

    AstralBear Active Member

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    I suspect the alternator has the short but I'm not sure , and there isn't a test for this at the store . If I was in a better money situation , I'd have gone out and bought a new alternator just to see if that's the problem. If it is , I'd have eliminated a lot of trouble shooting . It's been down for a week now .



    I'm gonna use the volatage meter tomarrow . I already made sure there was no corrosion and brushed all electric terminals with a small wire brush .

    Yeah , I had a car that had one . I thought about it being convenient .

    It has a surpentine belt and doesn't have the rubber bushings . But the problem does seem to be a faulty ground connection .
     
  9. AstralBear

    AstralBear Active Member

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    I drove to town two days ago and when I left to go home , needed to use jumper cables cause the battery was too weak to start . Drove home at night and when almost home the headlights got real dim for about two minutes than they got bright again .

    Their airconditions aren't so good either .

    All I have is a charge / discharge guage that either my eyesight is too poor to see it well or it hasn't moved in years .

    I'm gonna use a voltage meter tomarrow and try out all you suggested .

    Thanks
     
  10. HermitJohn

    HermitJohn Well-Known Member

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    I dont know what store you went to or how they do it in your area, but around here at least the AutoZone and O'Reilleys have a machine they mount your alternator on, put a belt on it and run it with an electric motor. They can check voltage and current output under load. Hmm, you know I've never taken a bolt down serpentine belt type alternator in, not sure how they would hook such up. Did they test your alternator on one of these machines or did they just use hand held tester in parking lot with alternator still in truck? The hand held testers can check voltage, but not sure that they can apply a load and test current output. So may well be bad alternator if thats the case.

    My Plymouth Arrow Pickup has Mitsubishi alternator wired just like GM Delco alternator with internal regulator. It gave problems of intermittant charging over a year ago. Sometimes it would, sometimes it wouldnt as shown by my built in ammeter gauge and the "screw driver test" mentioned by somebody else. AutoZone put it on machine and it showed good. Good voltage, good current output. Well had to be wiring but I had tried wiggling the wiring with no improvement. Dont have a manual for this truck so looked on internet and found wiring diagram for same Mitsubishi alternator adapted to some British sports car that originally had a generator. It showed using an "exciter circuit" also known as an idiot light just like the GM alternators. My alternator had this terminal but no wire connected on terminal and no idiot light for alternator so wasnt just disconnected or broken wire. It had come from factory this way. I connected up an old marker light socket and bulb under hood to this terminal on alternator and to a wire I found that is hot when key is turned on. Bulb lighted when key turned, then goes out when engine starts. No more problem. I assume there was suppose to be some sort of trace feedback current reaching the alternator to take place of the idiot light acting as an exciter in this application, but somehow that wasnt happening anymore or not consistantly.
     
  11. AstralBear

    AstralBear Active Member

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    The alternator was tested inside the store . The alternator is under warrenty . The policy of the store years ago would have been a replacement upon the customers dis satisfaction with the performance of the product .In other words , they used to trust the word of their customers .

    My memeroy isn't clear on this but years ago I brought back another lifetime warrenty alternator from another vehicle I owned at the same store , and if my memory is correct , I remember it tested OK on the machine but the guy at the store took my word over the machines test ( as if he knew this happens with their rebuilt alternators ) and the replacement alternator worked fine .

    Seems the store policy has change and replacements now needs the approval of a store manager FIRST .

    The NEW young manager who seems to know more about the advantages $ of sercuring commericial accounts for his store than he knows about Ford trucks and how to relate to customers , refuses to honor the warrenty . I thought it was rediculous that he's manager and needed someone to show him how to work the alternator testing machine . I think his education and " Interest " are geared more around business executive and climbing the corpoarte ladder than his interest in car mechanics .I was also informed that the managers get credit ratings on saving their stoe money by having less returned and replaced defective products that are lifetime warranted , which goes toward their annual evaluation that determines their yearly raise in pay .

    The only reason people get their parts in that store was because they were one of only two corpoarte auto parts stores around here that offer such a warranty and gave NO HASSLE when returning a part ( in the past ).

    I did notice that the store that was usually very crowed everytime I used to go in there years ago , was empty the 3 times I've been in there this last week .
    So I suspect others may be having trouble with their lifetime warranted JUNK parts .

    A little problem with a truck seems so much bigger when ones livestock depend on getting hay before a sno storm rolls in . I will never again buy bargin brand parts for my truck no matter how well the store baits their hooks with satisfaction of performance and warranty promises that they are starting to no longer honor .If it wasn't for a guy livng two miles down the road showing up this morning with his tractor carrying a round bale for my goats , I'd be feeding goats snow for the next 3 days .
     
  12. HermitJohn

    HermitJohn Well-Known Member

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    Tells me he may not have been capable of doing an accurate test although looks like those machines tend to be designed to be idiot proof as much as possible. Take alternator to a different store to be tested. If its faulty, up to you whether to hassle trying to get first store to honor their guarentee. Is there another branch of the first chain store you went to within reasonable distance? They should recognize the warranty on any part bought at that chain. Different manager there may know how to work the test equipment and honor the warranty.

    Some hate AutoZone and I'd be wary if it were a part that took lot work to remove and replace, but otherwise, I've had absolutely no hassles with getting warranty replacement. They are only suppose to replace things once under warranty, but I just took starter on Courier I used to have back every time it would go out. They'd look up on computer to check that I had bought it there and go get me another one. Must have gotten 5 or 6 starters. Manager even admitted they had a problem with their line of starters for imports. No problems at O'Reileys either. Dont have a PepBoys or AdvantageAutoParts so cant comment on them. Used to have a local chain called PoorMans. I liked them as prices were competitive and they carried higher quality parts. They could also get rare parts for old vehicles that bigger chain stores would just shake their heads at. Napa is usually good but pricey. But you never know, they were cheapest when I was looking for carrier bearing for my ex's old Datsun. I mean really significantly cheaper.
     
  13. agmantoo

    agmantoo agmantoo Supporter

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    Ford alternators have a diode inside that will short. I do not know the function of this diode I just know it is there. It is not part of the regulator circuit as to the regulators function during a test at the auto discount stores. When this diode I referenced shorts the alternator will test OK but if the vehicle sits not being driven the battery will drain. Obviously the remanufacturers do not test this diode. Just get a replacement alternator if this is the sysmptoms you are experiencing. When I return something that doesn't work and I know they are going to give me a hassel I am always certain it does work if you know what I mean.
     
  14. HermitJohn

    HermitJohn Well-Known Member

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    Learn something everyday.
     
  15. AstralBear

    AstralBear Active Member

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    Thanks agmantoo . My mechanic skills are limited , but from the simple wiring involved and everything else looking in good shape I feel strongly it has to be something wrong with the alternator .
     
  16. AstralBear

    AstralBear Active Member

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    I called Ford parts today to get a new pigtail connector for the alternator ,although I think the pigtail connector in the truck is good , it's 15 years old so I figured a new one will carry electric current more efficient ?
    .I told the Ford guy about my alternator testing OK on the auto parts store tester machine but it's not charging the battery . He said it's porbably burnt out diode's like agmantoo suggested .


    I went into the bargin store auto parts 3 times at different parts of the day with my alternator and with at least 6 people who work there hearing my problem , not one knew about diode's shorting out ???

    I found this web site about diodes and thought someone else may want to read it ?


    The paragraph says Motorola but I think the author ment Motorcraft ?
     
  17. Beeman

    Beeman Well-Known Member

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    Many Ford alts. do have diode problems that will draw the battery down, BUT these are usually the alts with an internal regulator. When auto repair becomes a guessing game it's time to STOP!. The aggravation, time and expense become more than it's worth. Proper diagnosis of the problem by qualified people is much cheaper in the long run.

    I get a good laugh out of the story about the parts store manager that's actually trying to make his store more profitable instead of the "try this part" exchange place for wannabe mechanics. When I ran my shop people would come in and tell me how they've changed all of these parts as per "the auto parts guy's advice". I would then ask them what the auto parts guy's job description was and what my job description was. His job is to SELL auto parts, and if he's doing his job you will have bought them. What should a parts counterperson know about fixing cars? The less they know the better off they are and the more parts you will buy in the guessing game.
     
  18. agmantoo

    agmantoo agmantoo Supporter

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    Beeman, the vehicle in question is a 1989 ford F-150 4.9 liter engine , straight 6. Am I not correct in that this truck has an internal regulator?
     
  19. dreadstalker

    dreadstalker Well-Known Member

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    check for a direct short
     
  20. AstralBear

    AstralBear Active Member

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    Well this wanna bee mechanic hit the nail on the nose .It's the alternator .


    I 'd give ya some advice , but I'd get banned for it .