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  1. #1
    Join Date
    Jul 2010
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    234

    Default Mystery device on Volvo 2001

    Hello,

    Could someone help in identifying or offering any info on what this device could be that is connected to the back of my alternator?

    I have a VP2001 1991 with a saildrive attached. I also know that the engine has that negative isolator that you can see in the photo.

    The device is connected via a fuse to the positive out terminal on the alternator and has another connection to that negative isolator.

    Couple more pics here http://s1159.photobucket.com/albums/p628/the_branflake/

    I also have a couple of earths going from the negative isolator to the block, is that correct??

    Just in the process of getting all this sorted. Ive not had the boat long, but what i can say is that the engine starts, runs, charges, Tacho works, warning lights all operate as they should and ive not noticed anything wrong. Although i've not done any testing to see if this isolator is working properly.

    I hope thats enough info.

    As always many thanks for any info
    Mat

  2. #2
    Join Date
    May 2005
    Posts
    634

    Default

    It looks like a fairly big electrolytic capacitor, though why it there & what it is doing, I have no idea.

    Others more familiar with the VP2001 may be along with a clue.

    edit. It looks like the negative isolator has been linked out with those green/yellow wires.

    I would be very tempted to pull that engine out & give it a little TLC, unless you have good access to sort things in place, while the saildrive looks clean, the engine looks like it has suffered a few leaks.

    The electrics look like they are on their last legs.
    Last edited by starfire; 06-04-12 at 11:06.
    This post is made from 100% recycled electrons.

  3. #3
    Join Date
    Nov 2001
    Posts
    516

    Default

    Suppressor (to prevent radio interference)?

  4. #4
    Join Date
    May 2005
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    634

    Default

    Quote Originally Posted by SimonD View Post
    Suppressor (to prevent radio interference)?
    I don't think so, normally a suppressor would be a small, say 1uF non polarized cap.

    But it was put there for a reason, judging by the (cleaner than the rest) crimps, recently, is it possible to ask the previous owner, who may have put it there ?
    This post is made from 100% recycled electrons.

  5. #5
    Easticks28 is offline Registered User
    Location : Norfolk Broads
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    Quote Originally Posted by starfire View Post
    It looks like a fairly big electrolytic capacitor, though why it there & what it is doing, I have no idea.
    Why would there be a fuse in the +ve to a capacitor?

  6. #6
    Join Date
    Jul 2010
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    Quote Originally Posted by starfire View Post

    I would be very tempted to pull that engine out & give it a little TLC, unless you have good access to sort things in place, while the saildrive looks clean, the engine looks like it has suffered a few leaks.

    The electrics look like they are on their last legs.
    Hi, Yeah i have fairly good access and have just finished working on the saildrive. The engine is my next target!!

    The last owner wasn't sure either.

    I think i need to check if that isolator is working this weekend. Also i did find some paper work for an inverter, could it be anything to do with this? The inverter was removed before i got the boat.

    Thanks for replies so far.
    Last edited by the_branflake; 06-04-12 at 16:46.

  7. #7
    Join Date
    Jul 2010
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    234

    Default Update

    It does appear to be a capacitor. On close inspection i can just make out something like 150 or 1500uf and a small RS stamp on the top.

    So what could its purpose be?

    What might i notice if its removed?

  8. #8
    VicS is offline Registered User
    Location : Home: Kent. Boat: Chichester
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    Quote Originally Posted by the_branflake View Post
    It does appear to be a capacitor. On close inspection i can just make out something like 150 or 1500uf and a small RS stamp on the top.

    So what could its purpose be?

    What might i notice if its removed?
    I can only assume it was added to overcome some radio interference problem. It may or may not have been effective.

    Id take it off.

  9. #9
    William_H is offline Registered User
    Location : West Australia
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    Jul 2003
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    Default Capacitor on alternator output

    Yes I agree it is probably an electrolytic capacitor fitted in an attempt to reduce radio interference from the alternator. Alternators don't usually cause a lot of radio interference. Usually a smaller value capacitor is sufficient. In this installation the long leads tend to provide inductance which stops the high frequencies being bypassed. The preferred style being a feed through capacitor which is cylindrical with a stud at each end. The body is earthed and the generator output goes to one end and out the other. The stud is just a continuous bolt. Or better still is a filter which has an inductance (choke) in line with the alternator output and appropriate small and large bypass capacitors on the input.

    Often however a badly interfering alternator has a diode dead so it will not charge full current (often not noticed) but means the output is syncopated with each AC cycle so makes interference.

    The fuse on the capacitor is because large electrolytic capacitors often have a failure mode going short circuit hence the good idea of fitting a fuse.
    OP can easily remove the fuse to see if it makes any difference. Check the fuse for condition (and the holder) as these fuse holders are not very reliable anyway. It may have disconnected itself long ago.
    good luck olewill

  10. #10
    nigelmercier's Avatar
    nigelmercier is online now Registered User
    Location : Live in Kent, boat in Canary Islands
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    What terminal does it go to?
    Nigel
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