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Thread: Alternator capacitor/noise filter necessary?

  1. #1
    Cubswede's Avatar
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    Alternator capacitor/noise filter necessary?

    I am doing some Heavy maintenance on my Engine, and when removing the alternator (Original alcor or motorola, dont know for sure because the dataplate is worn) I managed to tear out the lead that is soldered inside the Capacitor..
    Ok, I have to fix this, or do I? I dont know much about the reason its there..?
    Will there be alot of noise in the headsets if I just remove this, or would it affect the function of the alternator in another adverse way?

    There are no numbers on it, so I have no idea what to buy if I have to buy a new one. Found one here: http://www.aircraftspruce.com/catalo...lickkey=295439 But is seems quite expensive to me..
    Any advise would be appreciated
    982.JPG
    Last edited by SJ; 01-12-2017 at 08:22 PM. Reason: misspelling

  2. #2
    Cub Builder's Avatar
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    You may or may not need the cap. Often times they are installed in an attempt to fix the whining alternator noise either in your intercom, your radio reception or your broadcasts. Often times the issue is a weak or failing diode in the alternator, so the issue may have gone away if the alternator was replaced in the time since that cap was installed. I don't have a cap or filter of any kind on the alternator on either of my planes and don't seem to have any whine in the reception or transmissions. But both of my alternators are reasonably new. (<10 yrs old)

    If it was me, I'd go without the cap. If you have an issue, you can always buy the one form Aircraft Spruce to add back on.

    -Cub Builder

  3. #3
    wireweinie's Avatar
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    The bracket is from an InterAv alternator that was installed to replace the original generator. The capacitor in the picture looks like it was installed as an afterthought and was NOT part of the original kit. The best thing to do is find and repair the source of the noise so it does not need the capacitor (also called a 'filter' when installed like this). A filter of any kind just masks the noise, it does not cure anything.

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  4. #4
    www.SkupTech.com mike mcs repair's Avatar
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    actually i think thats a late 70's original piper interav install, that did have that.... ???

  5. #5
    wireweinie's Avatar
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    Well, there goes my high regard for Piper. InterAv....?!
    I just looked it up in a 1982 parts book. Figure 37, item 50, part number 758-080, should be the number for the capacitor. But in all seriousness, I wouldn't put an InterAv system back on. To many good choices of more dependable, less noisy systems to choose from.

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  6. #6

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    The spike guard takes a lot out.

  7. #7
    wireweinie's Avatar
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    That's just another filter. With good brushes in the alternator and the newer style electronic regulators (especially the linear styles) the noise won't be produced in the first place. That's the goal, to not have noise that needs masking.

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  8. #8

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    98 Geo metro 1 wire alternator, do a 337 and have an alternator that you can Source at any auto parts store. And the have been approved for years!
    Likes Dave Calkins liked this post

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