Generator Diode Replacement

• Aug 22, 2019

• #1

dtfeld

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Jun 5, 2016

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Milton, GA

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410 Sundancer
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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

 

Last edited: Aug 22, 2019

• Aug 22, 2019

• #2

dtfeld

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Milton, GA

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410 Sundancer
2001
12" Axiom and 9" Axiom+ MFD

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Cat 3126 V-Drives

Cross reference... Any reson this wont work??

 

• Aug 22, 2019

• #3

JimG

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Nov 4, 2008

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Southern WV

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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.

 

• Aug 22, 2019

• #4

dtfeld

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2001
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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...

 

• Aug 22, 2019

• #5

Stee6043

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Jun 1, 2015

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West Michigan

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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

 

• Aug 22, 2019

• #6

dtfeld

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Milton, GA

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410 Sundancer
2001
12" Axiom and 9" Axiom+ MFD

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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.

 

• Aug 22, 2019

• #7

mquiet

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I would be interested in how you figured out the diode had gone bad. Thanks.

 

• Aug 22, 2019

• #8

dtfeld

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2001
12" Axiom and 9" Axiom+ MFD

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Cat 3126 V-Drives

mquiet said:

I would be interested in how you figured out the diode had gone bad. Thanks.

Click to expand...

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

• Aug 22, 2019

• #9

PlayDate

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Dec 25, 2006

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dtfeld said:

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, a solenoid that was stuck in the made position, and finally that bad diode. It took me a month to sort it out.

Click to expand...

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!

 

• Aug 22, 2019

• #10

dtfeld

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410 Sundancer
2001
12" Axiom and 9" Axiom+ MFD

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Cat 3126 V-Drives

PlayDate said:

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!

Click to expand...

Thanks!

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

 

• Aug 22, 2019

• #11

JVM225

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Apr 8, 2008

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Dave is my tech hero. Wish I had his skills.

 

• Aug 23, 2019

• #12

dtfeld

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Milton, GA

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410 Sundancer
2001
12" Axiom and 9" Axiom+ MFD

Engines

Cat 3126 V-Drives

JVM225 said:

Dave is my tech hero. Wish I had his skills.

Click to expand...

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.