Westerbeke genset 8.0 btd won’t stay running

TRG

TRG

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Jul 20, 2022
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Vancouver, WA
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2000 SeaRay 400 sedan bridge
2011 Mastercraft X45 (for sale)
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I have been working today on my genset to get it running. It blows the 8amp fuse at the control box. I thought it was the oil switch at first, then the exhaust temp switch, but now not so sure. Looking at the wiring diagram they are wired in series first oil, then water, then exhaust. I started by unhooking all the wires from all 3 then plugged them in in order and fuse blows once last switch is hooked up. Now thinking that this is because it completes the circuit. I’m now questioning if it is any of the 3 switches or just the wiring? Any ideas on how to isolate the problem. If I have any of the 3 switches power unhooked I can start the genset because the fuse does not blow so then I can hold the down preheater and start the genie since it also bypasses the switches but then it dies when I let go of the preheater switch.
 
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I had a similar problem. Coolant temp switched shorted to ground. As they are not very expensive and you may want to have as spares, I'd just buy all new ones, install, and see if that cures the problem.
 
I also had the same problem i jumped the coolant switch problem gone
 
image.jpg
I pulled the diode out today and it looks ok but I’m not an electrician so just going by looks. I am not sure this is the issue
 
TRG said:
View attachment 132694 I pulled the diode out today and it looks ok but I’m not an electrician so just going by looks. I am not sure this is the issue
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Get your Digital Volt Ohm meter out and set it to measure resistance. Measure the resistance going through the diode one way then reverse the connection and measure going the other direction. One direction should be very high resistance and the other very low resistance, a check valve if you like. If they are both low resistance or both high resistance then it is kaput.
Electrons flow from positive to negative in a DC circuit or from the Anode to the Cathode. That stripe on the Diode is the cathode side and must be installed as it was removed.
OIP.fCou7rA7bue9oexJvjZlXgHaDQ
 
image.jpg
I made it back to check the diode. I am getting .004v in both directions so looks like this is my problem.

does anyone have an idea of the part # or where I might be able to find one of these locally?

I am also trying to double check my model of generator. I know it is either a 6.0 50hz or an 8.0 60hz by the spec sticker but not sure what version since they are listed separately on Westerbeke web page?
 
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TRG said:
View attachment 132889 I made it back to check the diode. I am getting .004v in both directions so looks like this is my problem.

does anyone have an idea of the part # or where I might be able to find one of these locally?

I am also trying to double check my model of generator. I know it is either a 6.0 50hz or an 8.0 60hz by the spec sticker but not sure what version since they are listed separately on Westerbeke web page?
Click to expand...
Should be the 60hz. Unless the genny was built for Europe
 
TRG said:
Does anyone have an idea of the part # or where I might be able to find one of these locally?
Click to expand...

Personally I go to Westerbeke and buy the stuff there. When having problem with mine I bought maybe 5-7 of them, knowing I might screw up a few (which I did).

https://westerbeke.com/Product/DIODE/035931

Probably same item, but not guaranteeing it
https://www.mouser.com/ProductDetail/Diotec-Semiconductor/BY255?qs=OlC7AqGiEDm4VU85xQTt8Q==

Thread on same.
http://clubsearay.com/index.php?threads/generator-diode-replacement.94608/

If you have a problem sourcing, send me a PM and I'll see if I can find my extras.
 
Here is a caution. That diode failed not necessarily because of itself; if one of the components it is tied to fails to ground it will take out the diode. If I remember correctly, this is exactly what happened on an issue @dtfeld was dealing with. Keep me straight here Dave.
 
Its a basic Schottsky diode.

The Westerbeke part # is 35931, and last I checked it was $35 plus shipping.

if your in a hurry, I think about any Schottsky diode that’s close will work and you can get 20 on Amazon for $6

—> https://www.amazon.com/20-Pieces-1N5822-Schottky-Rectifier/dp/B079KF9TVR/ref=sr_1_3?crid=NVGRHDJTSN0W&keywords=schottky+diode+3A&qid=1661604267&rnid=2941120011&s=industrial&sprefix=schottky+diode+3a,aps,50&sr=1-3

if you want the exact item cheaper I use digikey. —> https://www.digikey.com/en/products/detail/dcomponents/BY255/15282604
 
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ttmott said:
Here is a caution. That diode failed not necessarily because of itself; if one of the components it is tied to fails to ground it will take out the diode. If I remember correctly, this is exactly what happened on an issue @dtfeld was dealing with. Keep me straight here Dave.
Click to expand...

To be honest, I don’t really remember what the underlying issue was. It could have been one of the switches failed to ground, or vibration took its toll (I think that was the latest issue with the over temp switch).

Regardless, I would check that none of the switches are grounded out with a DVM just to be sure.

@ttmott is more of the the electronics guru, and may want to check my diode recommendations, but if you buy a pack of 20, you’ll have a lifetime supply even in the event this is more than just a diode issue.
 
I bought a new multimeter a took the cheep one back I originally purchased as it was giving me some bad readings I believe. With the new reader I am getting .6 reading on the diode when checking correct polarity and I get numbers jumping around when I check with the leads reversed I get around .04. Does this sound correct for a good diode?
 
Volts, amps Ohm's? Is the diode removed from the circuit? How/what are you measuring? Not clear.

Does your volt meter have a Diode test mode? If it does, try that.

https://www.fluke.com/en-us/learn/blog/digital-multimeters/how-to-test-diodes


However, based on what you've written, I'm about 99.9999% sure its the diode.

FWIW, I'd buy a couple of the diodes listed above , check to make sure none of the switches are grounded and replace the diode.
 
dtfeld said:
Volts, amps Ohm's? Is the diode removed from the circuit? How/what are you measuring? Not clear.

Does your volt meter have a Diode test mode? If it does, try that.

https://www.fluke.com/en-us/learn/blog/digital-multimeters/how-to-test-diodes


However, based on what you've written, I'm about 99.9999% sure its the diode.

FWIW, I'd buy a couple of the diodes listed above , check to make sure none of the switches are grounded and replace the diode.
Click to expand...
Yes was in diode test mode and diode was removed.
 
That's a bad diode... should show open in reverse polarity.
 
I received the diode part # from Westerbeke and it is #41081 for generator 8.0 btd, also same part # for 6.0 btd
 
Can anyone tell me how I test the switches?
 
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