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  1. #1
    Join Date
    Oct 2017
    Posts
    12

    Default Alternator not charging - intermittently

    Hi all, I have had an issue recently with my alternator.

    In the last week, it will be working one moment and then then it will stop charging the batteries. The first time it self corrected but now itís just happened again.

    I have checked the batteries and they are ok.

    There is 16v coming from the +ve and -be terminals of the alternator.

    Any hints where to check next? Would this suggest a faulty voltage regulator? Any way to confirm?

    It might be worth noting that I have a diode splitter. However both the service and starter batteries are not being charged.

    Many thanks in advanced!!

  2. #2
    Join Date
    Jul 2002
    Location
    Home: Kent. Boat: Chichester
    Posts
    43,425

    Default Re: Alternator not charging - intermittently

    Quote Originally Posted by lawrence_craig View Post
    Hi all, I have had an issue recently with my alternator.

    In the last week, it will be working one moment and then then it will stop charging the batteries. The first time it self corrected but now it’s just happened again.

    I have checked the batteries and they are ok.

    There is 16v coming from the +ve and -be terminals of the alternator.

    Any hints where to check next? Would this suggest a faulty voltage regulator? Any way to confirm?

    It might be worth noting that I have a diode splitter. However both the service and starter batteries are not being charged.

    Many thanks in advanced!!
    If there is 16 volts at the alternator but the batteries are not being charged there is something wrong or a bad connection between the two. If neither battery is being charged the fause of the trouble lies on the common part of the positive circuit or on the negative
    16 volts is high but probably indicates that the alternator is battery sensed .

    No reason to suspect the regulator

  3. #3
    Join Date
    Oct 2017
    Posts
    12

    Default Re: Alternator not charging - intermittently

    Quote Originally Posted by VicS View Post
    If there is 16 volts at the alternator but the batteries are not being charged there is something wrong or a bad connection between the two. If neither battery is being charged the fause of the trouble lies on the common part of the positive circuit or on the negative
    16 volts is high but probably indicates that the alternator is battery sensed .

    No reason to suspect the regulator
    Thanks for the response!

    I have just bypassed the diode and connected the Alt straight to the service batt. Alt now back to 14.4v and service at 13.8v and charging. So all fingers point at diodes no? Anything I should be aware of now Iíve bypassed the diode apart from monitoring the starter battery level?

  4. #4
    Join Date
    Apr 2002
    Location
    Cornwall
    Posts
    8,796

    Default Re: Alternator not charging - intermittently

    Quote Originally Posted by lawrence_craig View Post
    Hi all, I have had an issue recently with my alternator.

    In the last week, it will be working one moment and then then it will stop charging the batteries. The first time it self corrected but now itís just happened again.

    I have checked the batteries and they are ok.

    There is 16v coming from the +ve and -be terminals of the alternator.

    Any hints where to check next? Would this suggest a faulty voltage regulator? Any way to confirm?

    It might be worth noting that I have a diode splitter. However both the service and starter batteries are not being charged.

    Many thanks in advanced!!
    Try connecting the feed ( feed from alternator) at the blocking diode to a battery connection on the blocking diode, you then connect the alternator direct to a battery. Takes blocking diode out of the equation, if you have 12 volt at the alternator, check alternator, may be reg.

    Brian
    Kddpowercentre VASR charge

  5. #5
    Join Date
    Oct 2017
    Posts
    12

    Default Re: Alternator not charging - intermittently

    I think you guys have it. I bypassed the diode and connected the Alt to the Service Batt. Now getting 13.9v at service batt (charging) and 14.4v at alt.

    So it looks like the diode.

    Anything to be wary of whilst I am bypassing the diode? I will stop at the next marina and get a replacement (currently passage sailing).

  6. #6
    Join Date
    May 2016
    Location
    Suffolk
    Posts
    7,701

    Default Re: Alternator not charging - intermittently

    Quote Originally Posted by lawrence_craig View Post
    I think you guys have it. I bypassed the diode and connected the Alt to the Service Batt. Now getting 13.9v at service batt (charging) and 14.4v at alt.

    So it looks like the diode.

    Anything to be wary of whilst I am bypassing the diode? I will stop at the next marina and get a replacement (currently passage sailing).
    Only the service battery will be getting charged, the engine battery will not get a charge.
    Rainbow Marine.
    www.rainbowmarine.co.uk

  7. #7
    Join Date
    Apr 2002
    Location
    Cornwall
    Posts
    8,796

    Default Re: Alternator not charging - intermittently

    Quote Originally Posted by lawrence_craig View Post
    I think you guys have it. I bypassed the diode and connected the Alt to the Service Batt. Now getting 13.9v at service batt (charging) and 14.4v at alt.

    So it looks like the diode.

    Anything to be wary of whilst I am bypassing the diode? I will stop at the next marina and get a replacement (currently passage sailing).
    You still have a big volt drop, may be low battery and large current, keep an eye on it, you want to end up with 14.4 volt at the battery. if it stays low PM me your e-mail address and I will send you a data sheet on how to check where the fault is.

    Brian
    Kddpowercentre VASR charge

  8. #8
    Join Date
    Apr 2002
    Location
    Cornwall
    Posts
    8,796

    Default Re: Alternator not charging - intermittently

    Quote Originally Posted by halcyon View Post
    You still have a big volt drop, may be low battery and large current, keep an eye on it, you want to end up with 14.4 volt at the battery. if it stays low PM me your e-mail address and I will send you a data sheet on how to check where the fault is.

    Brian
    Check engine battery volts, if not good, connect alternator to engine battery, when engine running connect service attery lead as well, you are then charging all batteries.

    Remember to disconnect service battery when you stop the engine.


    Brian
    Kddpowercentre VASR charge

  9. #9
    Join Date
    Oct 2017
    Posts
    12

    Default Re: Alternator not charging - intermittently

    Quote Originally Posted by halcyon View Post
    You still have a big volt drop, may be low battery and large current, keep an eye on it, you want to end up with 14.4 volt at the battery. if it stays low PM me your e-mail address and I will send you a data sheet on how to check where the fault is.

    Brian
    I just tested. Service batt now at 14v and Alternator at 14.25v.

    Good idea around Starter battery!

    In terms of replacement, would you recommend another split diode or VSR?

  10. #10
    Join Date
    Jan 2011
    Posts
    5,707

    Default Re: Alternator not charging - intermittently

    Quote Originally Posted by lawrence_craig View Post
    I just tested. Service batt now at 14v and Alternator at 14.25v.

    Good idea around Starter battery!

    In terms of replacement, would you recommend another split diode or VSR?
    Simplest solution if you are replacing a diode splitter and want something better is the Sterling A to B charger. Quick simple change using the same 3 connections.

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