Edmunds Answers

Answers

  • MrShift@Edmunds 05/19/11 1:04 pm PST

    GEEZ NO, don't reverse polarity on an alternator system.


    Try the public library and see if they have a 1972 era MOTOR'S manual or Chilton's manual.

    THIS DIAGRAM may help you if you can print it out and read it okay.



  • Stever@Edmunds 05/19/11 1:54 pm PST

    You can reply in this thread by clicking the Answer this Question button and that will help keep all the information in one spot. Thanks!

  • zaken1 05/19/11 3:45 pm PST

    There are several different types of regulators which may be used on this model; some of those regulators have three terminals, and others have four terminals.

    Before dealing with the regulator issue; you need to have a heavy gauge wire (# 10 or heavier) connected between the battery positive terminal, or the terminal on the starter solenoid where the positive battery cable attaches, and the alternator terminal which is marked "battery." Without this power wire from the battery in place; the alternator will not function; no matter how it is connected.

    If you find that there is a spark when the battery cable first touches the alternator's battery terminal; this means the diodes in the alternator have been damaged. This usually happens if the alternator polarity was even briefly reversed. ALTERNATOR POLARITY CANNOT BE REVERSED WITHOUT DAMAGING THE DIODES. Whoever told you to reverse the polarity to make it charge was probably thinking of the old DC generators which were used before alternators came out. It was safe to reverse bias DC generators to make them start charging; but that trick will destroy alternators if it is tried. Ford switched from DC generators to alternators close to the time your truck was built.

    The regulator terminals are probably marked "B," "F," and "A." If there are only three regulator terminals and they are marked that way; the "B" terminal goes to a power wire from the ignition switch which is only hot when the key is on. The "F" terminal should be connected to the Field terminal on the alternator. And the "A" terminal should be connected to the armature terminal where the battery power wire attaches on the alternator.

    If there is a fourth terminal on the regulator marked "IG" it should go to the ignition switch power point where I previously said to connect the "B" terminal; and the "B" terminal should now go to the alternator battery terminal; along with the "A" wire from the regulator.

    If you bought your alternator from a discount parts store; it may be defective. There is an epedemic of poorly repaired alternators being sold by discount stores. If you got it from a wrecking yard; it also may be defective. It is all too common for an alternator to have been destroyed by improper connections. The only safe place I know of to buy rebuilt alternators is a NAPA parts store.

    If you want to respond to this question; please do not do so by opening a new question. Instead, just click on the "answer this question" link in this thread, type your response in the box that appears, and click the "submit answer" button. That is the only way people who have already responded to your question will be notified that a new response has been posted.

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