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Thread: adk4x4 : 715 Alternator Rebuild Project Series

  1. #1

    Default adk4x4 : 715 Alternator Rebuild Project Series

    715 Alternator Rebuild Project Series
    Post by adk4x4 on Oct 4, 2006, 10:00am

    I have begun the quest to reveal the "secrets" to the M-715 alternator and the "how to" for repair and rebuilding. In a series of posts I will try to give definitive insight into this magic box while going through the step by step process of rebuilding my own alt.

    The backstory.

    After a year long resto to a 67' 715 which came out pretty good, the alt stopped puttin' out. I took my 715 alt to a local shop which was proported to have mil-spec experience. After $200 and a revealing visit which uncovered the fact that this guy was a drunk and told me he replaced the internal batteries (is that like water cooled muffler bearings?) it worked for about a week. Having moved away from that area in the same month I didn't get a chance to through the alt through his front window.

    The present.

    Still wanting to "use" the truck it was periodically charged and run. During which time the main output wire was diconnected which probably led to the stator to be fried. I took the alt apart and tested it per the TM instructions. This is how it looks now, minus the volt reg.



    Each step in this process will include pics and diagrams so stay tuned for more to come soon.

  2. #2

    Default adk4x4 :

    Re: 715 Alternator Rebuild Project Series
    Post by adk4x4 on Oct 4, 2006, 11:22am

    Rectifier basics will be the focus of the first installments of the this series.

    The recitifier of the 715 alt is located mid section marked by cooling fins and the inability to remove them without complete disassembly. As shown in the manuals, two banks exist A, B or Pos, Neg. The rectifier is the simplest part of the alt and the easiest to test. This can be done with only removal of the back cover.

    Using a multimeter on diode test setting test across each diode. Open circuit in only one direction Best to remove the diode lead from the alt. Test the positive recitifier for discontinuity to the frame as well.

    Each bank consists of a heat sink/mount and three diodes. The diodes are 1/2" press fit automotive diodes.
    Cross reference # 1N3943 pos and neg anode or NTN5962 pos and neg anode, 25 amp and 400v ratings.

    here's a close up of both banks removed and diodes removed, note the rubber gasket/insulator be careful not to damage.



    Please note the positive bank is coated with epoxy and removal of the diodes may damage this coating and should be touched up.
    The wire tails have to be resoldered and this should be done while the diode is in the heatsink for stability and heat shedding.
    The next post will show the newly installed diodes.

  3. #3
    Join Date
    Sep 1998
    Location
    North Central Wisconsin
    Posts
    11,409

    Default brute4c :

    Re: 715 Alternator Rebuild Project Series
    Post by brute4c on Oct 4, 2006, 1:14pm

    GREAT STUFF!!!!

  4. #4
    Join Date
    Dec 2003
    Location
    SF Bay Area, CA
    Posts
    499

    Default hiker :

    Re: 715 Alternator Rebuild Project Series
    Post by hiker on Oct 4, 2006, 2:04pm

    Thanks for the write-up!

  5. #5

    Default adk4x4 :

    Re: 715 Alternator Rebuild Project Series
    Post by adk4x4 on Oct 6, 2006, 8:31am

    At last the parts are in! And they fit too!

    One thing I forgot to mention about removal of the recitifier, be careful to watch out for the isolation washers and bushings, these items will not be easy to replace.

    The removal of the old diodes was pretty easy. An old chisel and a few whacks later and out they came. I should have been a little more careful about though because now I will be touching up the epoxy coating on the heat sink.

    The new ones went in as easy. Do yourself a favor and check and double check that the pos. and neg. banks receive the correct diodes. I used a very large C-clamp and my benchtop to press them in. Use caution not to deform or distort the diode. A 3/8" socket fits perfectly over the diode on it's face and provides a flat surface to press on. The leads were cut off the old diodes and fitted to the new ones. The factory used a bronze clip, no solder, I used a spade connector cut in half and just a touch of solder. Be careful not to heat the diode. Mount the diodes first and then connect the leads.



    Now the recifier is ready for any epoxy touch-up on the pos. bank and re-install.

    The diode supplier was cpcares.com

  6. #6
    Join Date
    Sep 1998
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    North Central Wisconsin
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    Default brute4c :

    Re: 715 Alternator Rebuild Project Series
    Post by brute4c on Oct 6, 2006, 9:12am

    How I wish I hadnt thrown away that one alternator that the diodes went bad on....

    Great writeup!!!

  7. #7

    Default adk4x4 :

    Re: 715 Alternator Rebuild Project Series
    Post by adk4x4 on Oct 6, 2006, 9:19am

    The second installment of this series shall be the stator rewind.

    After close examination it was clear that the stator (the stationary coil of wire mounted in the frame of the alt, pictured in the bottom left of the first photo) was fried. The varnish was burned off the wires and they were black. The stator is wound in a delta 3phase configuration and each of the three coils of the winding is 18ga two-wire, 7-turns/tooth, 12 tooth design.

    I am attempting to provide diagrams and such for clarity of the electrical speak.

    So far I have stripped the wire from the core. If attempting to do this be sure you're ready to take some time and get a few blisters, caution besure to mark the beginning of the windings in the core, this can be figured out but better to be fool proof.



    Like the recitier the stator also has epoxy on the ends to protect the windings making the turns. This will likely not survive the stripping process, and will require replacement.

    I have ordered the replacement magnet wire (winding wire with integral insulation coating for motors and generators) from a supplier. The standard insulation rating is 155oC, I suggest getting the 200oC wire for a few bucks more.

    More on all of this later.

  8. #8

    Default adk4x4 :

    Re: 715 Alternator Rebuild Project Series
    Post by adk4x4 on Oct 16, 2006, 4:31pm

    Just an update!

    The stator core has been epoxyed and painted with dialectric paint. Sorry no pics this time.

    Winding the new wire is a challange for even the most patient. The design of the core makes this part of the project the longest to deal with.

    The rectifier has been re-mounted into the frame and sealed with silicone as per the factory. An interesting note, the wires from the stator to the rectifier were siliconed for weatherproofing, the way it is applied is baffling it looks like a perfect bead with the wire perfectly embedded inside of it and they don't touch inside the bead. This will be hard to reproduce, mine won't look as pretty as the factory's, but will due none the less.

    Pics on the way. I will get the rect's and partial stator tonight.

  9. #9

    Default adk4x4 :

    Re: 715 Alternator Rebuild Project Series
    Post by adk4x4 on Oct 17, 2006, 10:55am



    As I said, this requires a lot of patience. I just spoke to my local "expert" motor shop and he said that even his best winder would opt out of doing this one.

  10. #10
    Join Date
    Sep 1998
    Location
    North Central Wisconsin
    Posts
    11,409

    Default brute4c :

    Re: 715 Alternator Rebuild Project Series
    Post by brute4c on Oct 17, 2006, 4:53pm

    Beautiful work!!!

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