Fuse blowing in Alternator Positive


  • Morning all.  I have had my WS 500 a year now, performed faultlessly.  Ran up the engine today during winter idle period and the Alternator Positive fuse has blown.  Replaced it, same again.  Alternator positive (big Prestolite alternator) not touching ground.  Any ideas please?


  • What is the value from the fuse that is blown? As a test, check or there is a problem inside the alternator. Do this test, which Al Thomason posted in this forum before. \"\"Remove the Blue Field wire from the alternator (Please be safe here), make sure the batteries are around 60-70% SOC or less, and then while the engine is running BRIEFLY touch the Field terminal (edit BEN: the FIELD wire that goes to the alternator, NOT the blue to the regulator) on the alternator  +12v.     You should be able to hear the engine loading and notice amps being delivered.\"\" Have a amp clamp meter around this wire at the time off testing, to see how many amps flow through your field inside the alternator.  As a extra safety use a 15amp, fuse between the \"alternator field\" AND \"alternator +\" when you do this test.   Let us know the result from this test. IF you have no amp clamp meter, do the test with a 10amp fuse in line, does the fuse trips? How much amps you see on your system battery monitor at the time from testing?      

  • Ben has some good ideas and I think he is correct in suspecting your alternator is the problem.   Second step after that would be to check the wires inside the AMP connector for chafing.  If neither of these gets you to an external problem, and it does it sounds like you may have bad reg you will want to reach out to Wakespeed. Wakespeed used to have a board replacement program but since they were purchased last year by Dragonfly they have not shared their new procedures.  You can contact them directly here:    https://www.wakespeed.com/contact/

  • Good morning.  Test conducted as far as I was able.  The battery bank is 1500 ah at 24v so I wasn\'t able to deplete it however connecting the field and positive resulted in engine loading and current flow at 1200 rpm of 37 amps which is normal, its a 150 amp alternator but we only used 12oo revs.  I used a 20 amp fuse in the connection which was fine during the test.  The size of the spark on connecting and disconnecting was small and didn\'t very according to revs of the engine.  A guess would be 5amps flowing.  Is it as Rick says a return issue?  I bought the unit through Offgrid a few days over a year ago.   Is it still under warranty please? POSTSCRIPT.  After conducting the test I reconnected everything as normal and thought I would check at what point the fuse blew (it\'s a 20 amp as that\'s all I have where I am) and the system worked as normal, the only difference being the max charge current was 28 amps but assume that\'s because the regulator was operating.  The only change to the original fault condition was the difference in time taken to raise the revs.  It\'s a critical part of the boat equipment so I am reluctant to say everything is fine until I am sure.   No other changes were made and the wiring wasn\'t moved.  Any advices much appreciated.  

  • If the blown fuse is not continues happen, it will be difficult to say what \"had\" blown the fuse before.   I never have seen a problem in the WS500 that has blow the fuse.   Rich mention the cable, I have not seen a problem with it. But if thd fuse blow again you could check or there is a problem in the cable. To check this, remove the fuse, disconnect the multi connector from regulator, put back the fuse.  If fuse dont blown, problem is not in the cable. (Always have the fuse alt+ and V-sense fuse removed before unplug the multi connector)   As the problem is not there, it is difficult to say what blows the fuse.  I would check the alternator field cable to the brushes first.  I really think that the problem is not cause by the ws500cable and ws500 unit.  

  • Thanks Ben,  really strange yes, two fuses blew now nothing.  I will check the cabling once more but it is in very good condition, zero corrosion and dry. Really appreciate your help.  just in case, what is the warranty period on the WS 500 please?  Cheers  

  • Warranty is 2 years.  Best to contact Rick by email. Iam ws500 dealer in Asia. Iam not sure how they handle a warranty issue as this. If the unit is bench tested all could be ok. Many companies send the unit back to you.   With my view on your problem and with my knowledge from alternator installations and knowledge on pcb device level.  I think the problem is for 99% in the cable or alternator.  Not inside the device. Discuss with Rick what to do My view: 1 check inside alternator. 2 check inside multi connector OR replace multi cable completely. If still not solved replace ws500          

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