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Thread: How To: Delorean Factory Motorola Alternator Restoration

  1. #1
    G'SCHEIDELE jcrubin's Avatar
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    How To: Delorean Factory Motorola Alternator Restoration

    While Elvis and I were working on the car cleaning grounds and connection in an attempt to solve for some electrical issues, i'd noticed a visual indication that there was trouble with the alternator. No doubt potting material is deteriorating. This alternator will need to be removed for evaluation and repair.

    With a standard de-installation and a minimal amount of mistakes; having the unit on the bench we see that there will be some issues with loosening screws that have galvanic-ally corroded over the years. Some are a lost cause as we see with the capacitor, needing to be ground down and machined later.

    With that out of the way, removing the removal of the plastic shroud makes it clear that most of that potting material has ended up in the cooling fins of the lower side of the rectifier. Cleanup, if possible, will be extensive. It was almost no surprise, but still quite amazing that the voltage regulator was all but empty, having completely melted out.

    I spend some time with the shroud and various chemicals to see what responds to the residue. Turns out throttle body cleaner seems to have an effect on it.

    Next I remove the the nut and pulley with standard tools and procedures ensuring everything stays in order. This is followed by the brushed, which I have about a fifty percent success rate removing the screws. The brushes removed however looked surprisingly good, i will most likely reuse them.

    I then remove the four bolts that secure the assembly, and the 3 screws that hold the front bearing into the race. Though, I'm running out of special alternator tools, so, its off to Jason for some special tools for the job.

    Behind the scenes there were some discussions about how to remove certain things without damage, some procedures were standard fare. Some setups for pulling bearings out of the races were total custom setups. Both bearings, upon inspection, were more than ready for replacement.

    Once separated cleaning was started, the front cover was sand blasted. After that, all of the broken screws were drilled out on the press. It was then cleaned with a variety of chemicals. Brought home the last hole was tapped to 4mm and the brushes test fit.

    At this points with two new bearings ordered we end this episode here and wait for parts arrived for test and assembly in the next episode.


    Jordan 011613

    "CVM CATAPVLTAE PROSCRIPTAE ERVNT TVM SOLI PROSCRIPT CATAPVLTAS HABEBVNT!!"

  2. #2
    G'SCHEIDELE jcrubin's Avatar
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    The second half of the video continues off with the disassembled,cleaned and stripped factor alternator of the Delorean. With the bearings arrived I toss them in the freezer while I prepare. I removed the sticker on the side before going down to the bug ranch so it would not get damaged. Starting off, the entire housing was taped off. Since it cant be sand blasted, I opted for a wire brush on a drill press to clean up the aluminum. I also used to to break up the dullness of the blasting on the top cover from last video.

    I prep the press for the installation of the bearings, starting with the top cover first. Using original NTN bearing 6203LLU. Minor lubrication of the race was done to stop any galling. with the bearing installed I tape and prepare with acetone for clear coating, with high-temp clear coat. I them prep the bottom portion for bearing installation this time with bearing 6200-2Z as well. The bottom is also prepped and clear coated in the same manner.

    While the two main housings were drying I sandblasted all of the brackets nuts and bolts and sanded the ground of the capacitor. After this the bearing retainer was reinstalled with blue locktite. The rotor was then pressed into the top cover bearing to full seat. I stopped there because I wanted to do a few things, I nickel plated all of the small parts, also, I wanted to varnish the exposed wires of the rotor, so I took some time out to do so.

    Back at the shop I take time to discuss what I feel would have been the correct disassembly procedure for video 1. This would have been with the bolts removed first tapping out the back smaller shaft through the small hole with a drift, and then leaving the front bearing retainer alone, pressing the rotor out of the top housing.

    Continuing, I apply a thin coat of anti-seize to the circumference of the top of the mating surface of the main housing. The halved are brought together on the press and pressed together only slightly so the top still rotates, then removed from the press so that the bolts can go through as a guide, back on the press and brought to full seat. Off of the press the four bolts are tightened down with blue locktite.

    The brushed are reintroduced into the unit, all screws receive anti-seize, this is followed by the installation of the new voltage regulator, and then the plastic shroud. With that the front parts for the fan and pulley are reassembled to the alternator. The nut up front got blue locktite on the threads and was torqued to 30ft/lbs

    At this moment I realized I never checked the capacitor and realized it was bad so I had to stop and over one from England. Once it arrived I installed it and the alternator was ready for installation. This is done in the reverse process as removal though the main mounting bold is covered with a light coat of anti-seize. Once the installation is completed the car is started, monitoring only the mechanical portion of the work. Noises, breaking things, fires and whatnot.


    Finally, everything is tested with the fluke meter under a variety of loads connected to the battery terminals. This, with a weak batter, using a combination of internal fans, headlights, and cooling fans showed that while the alternator doesn't pack a punch, it has significantly improved with this restoration calling the work a success.


    Jordan 011613

    "CVM CATAPVLTAE PROSCRIPTAE ERVNT TVM SOLI PROSCRIPT CATAPVLTAS HABEBVNT!!"

  3. #3
    G'SCHEIDELE jcrubin's Avatar
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    From rafael

    Along with a Gates 7485 Belt

    https://www.amazon.com/gp/product/B0...Q-iHe_TrntHoPY
    Jordan 011613

    "CVM CATAPVLTAE PROSCRIPTAE ERVNT TVM SOLI PROSCRIPT CATAPVLTAS HABEBVNT!!"

  4. #4
    Administrator Ron's Avatar
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    ...Moved to How-To Guides

  5. #5
    Delorean Guru
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    Where did you order the parts, what part numbers did you use, was it a kit, and what did it cost? If it was a kit what was included?
    David Teitelbaum

  6. #6
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    Quote Originally Posted by David T View Post
    Where did you order the parts, what part numbers did you use, was it a kit, and what did it cost? If it was a kit what was included?
    I think he replaced individual items - for sure the Regulator, brushes, bearing and capacitor.

    Regulator:
    https://www.ebay.com/itm/REGULATORS-...72.m2749.l2649

    Brushes:
    https://www.ebay.com/itm/Brush-Holde...item1a7a36fc76

    Capacitor:
    https://www.ebay.com/itm/Capacitor-f...72.m2749.l2649

    And I can't remember the specific bearing types...but I'm sure Jordan can chime in.

  7. #7
    Delorean Guru
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    I am looking for a kit but if I have to, I will order the parts individually. The bearings are 6203 and 6200. Does anyone know the numbers on the label? I am having trouble reading the label on my alternator, some of the numbers/letters are unreadable. Mainly the type number is what I need.
    David Teitelbaum

  8. #8
    Delorean Guru
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    The Motorola alternator is a Type 9AR 2938T. The bearing numbers need to be confirmed, Pretty sure about the 6203, not sure about the 6200. I haven't found kits for the alternator so it looks like you have to order the parts individually. Before I order the parts I will disassemble the old one to confirm the bearings. The general consensus is to not even try to fix the original alternator. Unless you are concerned about originality the recommendation is to replace it with a newer, higher output alternator. Very easy to do with minimal (if any) modification.
    David Teitelbaum

  9. #9
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    Bearings are confirmed 6203 and 6200. On my alternator I saw goo dripping out and thought my voltage regulator failed like in the pictures. Very common. Once I got it apart the voltage regulator looked like new. The goo came from the rear (6200) bearing and got into the diode bridge. Lacquer thinner cleaned it all up. Do NOT try pushing out the rear bearing with a punch. The hole is very small and the thin punch just bent. Ordered thetwo bearings and a brush holder assembly. I couldn't find anyone selling kits so they had to be ordered individually. Be careful buying the bearings. Do NOT get Chinese bearings. Pay a little more and get something good like nos SKF or Timken. My capacitor tested good and I also checked the diode bridge, rotor and stator. The alternator was working well when I took it out so I didn't expect anything to be wrong with it electrically except the regulator going bad. To clean the diode bridge I had to unsolder it and remove it. Good exploded picture and procedures in M:05:02-04 and 3-2-0. Getting a smaller pulley to "overdrive" the alternator so it can put out more at idle is not a great idea. You do not want to overspeed the alternator at high RPM's. The battery is supposed to be able to sustain the electrical system for the short period the car may be idling. The alternator is sized to provide enough power to handle all of the car's loads with a little left over to charge the battery. In theory the battery is only supposed to provide enough power to start the car. Once started the alternator just has to put that power back. The battery also provides power during any short time the alternator can't handle all of the loads like when idling. Finally the battery is there to smooth out any pulses and transients on the electrical system like the fans starting and the fluctuating DC output from the alternator. In practice it is better to oversize the alternator so it doesn't have to work hard at it's full rated output. Doing that for prolonged periods of time takes a toll on an alternator's longevity. It is even worse on a car that is only used occasionally. The battery is always undercharged so the alternator has to work that much harder. Using a battery tender to keep the battery fully charged makes it a LOT easier on the alternator.
    David Teitelbaum

  10. #10
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    Finished assembling the alternator and installed it. My advice for anyone attempting to rebuild either the Motorola or the Ducy is, it is not worth it. Even when working perfectly they are marginal at best (the Ducy even more so). The Delorean vendors don't have parts and encourage outright replacement with something more modern and powerful. Good advice. Easily done with minor to no modifications necessary. The only good reason to keep the original alternator is for originality if that means anything. For the record the Motorola is a 9AR. The front bearing is a 6203 and the rear is a 6200. The suffices are for the seals in the bearings and they really don't matter much in this application. The brushholder and the regulator is generic and available. If the rotor or the stator or the diode bridge is bad it doesn't pay to rebuild. I spent about $20 for the two bearings and the brushholder. The assembly and disassembly were pretty straightforward as described in the video. A replacement alternator is over $200 but you do get a better alternator.
    David Teitelbaum

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