Generator Diode Replacement

Discussion in 'General Maintenance/Repair Questions' started by dtfeld, Aug 22, 2019.

  1. dtfeld

    dtfeld Water Contrails

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    Axiom 12 MFD
    Cat 3126 V-Drives
    I had a diode in my generator control box give up the magic smoke ( see post with schematic here http://clubsearay.com/index.php?threads/7-6btd-blowing-8a-fuse-part-3-bad-diode.94335/).

    I ordered a new one from Westerbeke for $30. I'd like to have some extra extra on board but not at $30 a piece. The new one from Westerbeke is a diode marked BY255 and had a slanted HY below it. Will any BY255 diode be an acceptable?

    I have found BY255 diode for a $0.25 a piece...

    Dave

    20190822_080909.jpg 20190822_080915.jpg 20190822_080921.jpg
     
    Last edited: Aug 22, 2019
  2. dtfeld

    dtfeld Water Contrails

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    Axiom 12 MFD
    Cat 3126 V-Drives
    Cross reference... Any reson this wont work??

    Capture1.PNG


    Capture.PNG
     
  3. JimG

    JimG Well-Known Member SILVER Sponsor

    Nov 4, 2008
    Southern WV
    2007 310 DA
    Kohler 5ECD
    Twin 350 Mags
    Raw Water Cooled
    V-Drives
    Yes, any BY255 diode will work. The HY is a manufacture symbol... several companies make a BY255.

    The NTE639 also looks like a suitable alternate.
     
    dtfeld and carterchapman like this.
  4. dtfeld

    dtfeld Water Contrails

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    Axiom 12 MFD
    Cat 3126 V-Drives
    I thought I’d try the local electronics parts store for some extras before installing the $30 Westerbeke part. I couldn’t find the exact diode but found a similar one, with a 3A 1000V rating for $1.99.

    I installed it and everything is back to running as it should. I kept the Westerbeke part, considering returning it...

    The cheap version...

    D45E39D1-669E-4299-ADB6-73F0F7423D5B.jpeg
     
  5. Stee6043

    Stee6043 Well-Known Member

    Jun 1, 2015
    West Michigan
    1997 Sundancer 400
    7.4L Gassers
    On a scale of 1-10 how painful was this project for you? Were you able to get to the diodes without removing your strbrd vacuflush system? Did the whole front end of the generator have to come off?

    Asking for a friend :)
     
  6. dtfeld

    dtfeld Water Contrails

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    Axiom 12 MFD
    Cat 3126 V-Drives
    The diode in question was in the control box, not the generator section. It fed the fuel lift pump during the preheat/start cycle on a westerbeke diesel generator. So I don’t think I can answer your question.

    According to Westerbeke there are 6 of these in the generator (I assume 1 in the control box and 5 in the generator somewhere). The lesson is you can source a dozen of these diodes for $5, instead of $150 from Westerbeke.
     
    The Bill Collector likes this.
  7. mquiet

    mquiet Well-Known Member

    Aug 4, 2009
    North carolina
    1999 480 Sedan Bridge
    Caterpillar 3196
    I would be interested in how you figured out the diode had gone bad. Thanks.
     
    dtfeld likes this.
  8. dtfeld

    dtfeld Water Contrails

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    Axiom 12 MFD
    Cat 3126 V-Drives
    Thats easy!! I smelled it burning...

    But on a more serious note, I looked at the schematic. It was obvious once I looked at what should be powered and what wasn't working. There were several issues with my generator, a high temp switch that had failed to ground, the preheat solenoid that was stuck in the made position, and finally that bad diode. It took me a month to sort it out.
     
    Last edited: Aug 22, 2019
    techmitch likes this.
  9. PlayDate

    PlayDate Well-Known Member

    Dec 25, 2006
    Washington DC
    1994 370 Express Cruiser
    454 Mercruisers
    That is impressive diagnostics considering two of the three weren't related to each other. The temp switch would have shut it down, the diode would have prevented it from making voltage. I'm not sure what solenoid you are referring to.

    Good work!
     
  10. dtfeld

    dtfeld Water Contrails

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    Axiom 12 MFD
    Cat 3126 V-Drives
    Thanks!

    The Preheat solenoid...I added some detail above. I think once the temp switch grounded out, it caused a cascade of other failures.
     
  11. JVM225

    JVM225 Well-Known Member GOLD Sponsor

    Apr 8, 2008
    Farmingdale, NY
    2002 410 Sundancer, Monaco Edition.
    3126 Cats.
    Dave is my tech hero. Wish I had his skills.
     
    carterchapman likes this.
  12. dtfeld

    dtfeld Water Contrails

    Jun 5, 2016
    Milton, GA
    410 Sundancer
    2001
    Axiom 12 MFD
    Cat 3126 V-Drives
    Thanks for the compliment, but I have to give a shout out to the CSR membership. I’ve learned a ton reading and communicating with this group. A little research on here and some persistence will get you a long way to solving a lot of issues.

    Hopefully, some of this will assist the next person dealing with these issues.
     
    JVM225 and Cocktail Time like this.

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