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  1. #21
    Join Date
    Aug 2019
    Posts
    12

    Default Re: What is this in my engine bay?

    Maybe itís a smoothing/spike/noise filter? Boat has a JRC RADAR so maybe itís a filter??

  2. #22
    Join Date
    Jul 2002
    Location
    Farnham, Surrey
    Posts
    21,407

    Default Re: What is this in my engine bay?

    The black domed thing is a transformer. I've worked with identical ones in different circumstances.

    This means that it's a home made inverter or similar. Does the alternator have a separate connection through to the battery or does the main feed from the alternator to the batteries only go 'through' this unit?
    Semper aliud

  3. #23
    Join Date
    Aug 2019
    Posts
    12

    Default Re: What is this in my engine bay?

    Hi there. There is only one output from the unit, being a large gauge brown cable. Iím going to trace that to see if goes direct to battery.

  4. #24
    Join Date
    Aug 2019
    Posts
    12

    Default Re: What is this in my engine bay?

    Quote Originally Posted by john_morris_uk View Post
    The black domed thing is a transformer. I've worked with identical ones in different circumstances.

    This means that it's a home made inverter or similar. Does the alternator have a separate connection through to the battery or does the main feed from the alternator to the batteries only go 'through' this unit?
    Just to confirm, only source out of alternator is through the unit (large positive cable).

  5. #25
    Join Date
    Sep 2019
    Posts
    9

    Default Re: What is this in my engine bay?

    Quote Originally Posted by Swenns Dad View Post
    Maybe itís a smoothing/spike/noise filter? Boat has a JRC RADAR so maybe itís a filter??
    Do not think itís a regulator, not enough connections. No connection to alternator field ?
    Again with a negative connection cannot see it being a diode splitter. And where is the connection to the second battery?
    If anything, and itís a big if, it might be some sort of filter/ suppression unit. The ďtransformerĒ might be an inductor (choke), although at the frequencies that are normally needed to be suppressed it would be a lot smaller. However the connection, in, out - and ground would make sense.
    First post so please forgive if this arrives a little late !
    Richard

  6. #26
    Join Date
    Aug 2019
    Posts
    12

    Default Re: What is this in my engine bay?

    Quote Originally Posted by Rich T View Post
    Do not think itís a regulator, not enough connections. No connection to alternator field ?
    Again with a negative connection cannot see it being a diode splitter. And where is the connection to the second battery?
    If anything, and itís a big if, it might be some sort of filter/ suppression unit. The ďtransformerĒ might be an inductor (choke), although at the frequencies that are normally needed to be suppressed it would be a lot smaller. However the connection, in, out - and ground would make sense.
    First post so please forgive if this arrives a little late !
    Richard
    I agree. It must be a filter, suppressor. Probably removes any AC on the DC line. As you say, if it was a regulator there should reasonably be another line feeding back to regulator.

  7. #27
    Join Date
    Jul 2002
    Location
    Farnham, Surrey
    Posts
    21,407

    Default Re: What is this in my engine bay?

    Quote Originally Posted by Rich T View Post
    Do not think it’s a regulator, not enough connections. No connection to alternator field ?
    Again with a negative connection cannot see it being a diode splitter. And where is the connection to the second battery?
    If anything, and it’s a big if, it might be some sort of filter/ suppression unit. The “transformer” might be an inductor (choke), although at the frequencies that are normally needed to be suppressed it would be a lot smaller. However the connection, in, out - and ground would make sense.
    First post so please forgive if this arrives a little late !
    Richard
    I thought there was a slim possibility of it being a choke as well, but it would be so unusual to have a choke of that size that I discounted it and chose to treat that possibility as vanishingly small.

    If it's a filter, then the DC resistance between the input and the output should be very very low. It can easily be checked with a multimeter.

    Alternatively, just remove the device from the charging circuit and see if the alternator starts to work properly.

    Another test would be to ensure that there is full battery volts appearing on the main output of the alternator when the engine is stopped. With the batteries 'on' the +Ve terminal on the alternator should be a direct connection straight through to the battery positive.
    Semper aliud

  8. #28
    Join Date
    Sep 2019
    Posts
    9

    Default Re: What is this in my engine bay?

    Quote Originally Posted by john_morris_uk View Post
    I thought there was a slim possibility of it being a choke as well, but it would be so unusual to have a choke of that size that I discounted it and chose to treat that possibility as vanishingly small.

    If it's a filter, then the DC resistance between the input and the output should be very very low. It can easily be checked with a multimeter.

    Alternatively, just remove the device from the charging circuit and see if the alternator starts to work properly.

    Another test would be to ensure that there is full battery volts appearing on the main output of the alternator when the engine is stopped. With the batteries 'on' the +Ve terminal on the alternator should be a direct connection straight through to the battery positive.
    +1, thatís certainly what I would do. The ďchokeĒ may be that size because of the heavy windings used to support the expected high through current.

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