Westerbeke Diode Replacement - Help

M

mikenewhouse

Member
Apr 29, 2013
38
Kansas City
Boat Info
1999 400DA
Engines
7.4 HORIZONS
So this weekend our Westerbeke 7.2 stopped making power. Runs great just now AC output.

I have read everything I can find and everything points to the Cap the Diodes.

Today we went out and after an hour of messing around we were able to remove the Cap but for the life of me I cannot figure out how to get to the Diodes.

I know where they are, but think it is crazy that I would have to remove the whole metal backend to get to them.

Is there an access panel I am missing? or do I really have to unbolt the rear end from the engine? I am guessing its the four bolts near the middle of the genset. Will the rotor and stator stay put when I pull that whole thing apart ?

Any help would be greatly appreciated.
 
I have the 4.5 BCG with the same problem.

Did you test your genny after replacing the capacitor? I'm hoping that it's JUST the capacitor and not the diodes as well. A lot on the forum have mentioned just replacing the capacitor so i was wondering if you had tested after the swap.
 
Waiting for the Cap to arrive, should be here later this week and I will definitely try it first and report back. I hope as well that it is just the Cap.

The Cap has expanded pushing the top up about a quarter of an inch on one side so it is likely bad.
 
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OK, thanks for the heads up. Post back to the thread when you get the new one installed.
 
My Westerbeke has a hidden breaker switch on it. One weekend I popped it and that I was buying a new unit. Somebody told to look for the switch, found it, reset it and everything was great....
 
You know the old joke that goes, "You can't get there from here?" Yes?

I had a water intrusion problem with my genny, from the photo's EXIF data, about 10 years ago.


The diodes are soldered to the armature on the side of the alternator furthest from the engine. They are not easy to reach and some disassembly is required. And probably removing the genny from the boat, as well.

This is a gas Westerbeke, but the diesel is similar. On the far left of his image is the coupling housing that connects the alternator to the engine. Right behind it is the alternator section. I didn't paint the armature, so it's not pictured.

download


If I remember correctly, you can uncouple the generator from the engine by removing those four bolts that you see in the photo on the adapter part. You can see the bolts in the photo as I painted them. Once removed the alternator housing will come free from the engine. The armature will stay attached to the engine's flywheel by the coupling. Support the armature as soon as you can get the clearance to do so. The parts are heavy so it's a cumbersome task.

That said, I doubt the diodes are your problem. I recall looking at the rectifiers and noting that the rating on them was well more than necessary. But since you asked... This is how you do it.

Now, more likely there are a couple of fuses on the generator that could be a problem. There's also a circuit breaker for the A.C. power output. I'd first recommend checking the fuses and breakers because they are the most likely cause of your problem. If they're fine and the breakers are on, the I'd check the capacitor. The generator is of the self-exciting type and the capacitor forms a tuned L-C circuit with the generator's winding to power the rotating field armature. It's a good design for a boat because it's brushless. It's main disadvantage is the voltage regulation is a little looser and the output power is a bit noisy.

You know... noisy.
download


Anyway, the cap is far more likely a problem than the diodes. But note that under most failure modes, a failed cap usually first causes a very low voltage problem as the L-C goes out of tune. Likewise, there are multiple diodes, so a low voltage should occur first when the first diode fails.

After checking the breakers and fuses, see if there's any voltage at the panel. It's a diagnostic aid to know if you have 0 VAC or 40 VAC.
 
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FC3
Great info - however the pics did not come thru.

We have checked every fuse and every breaker on the boat and gen, both on the AC and DC side. All test good.

As stated in an earlier thread, the CAP has expanded and pushed the top almost all the way off, I tested it with my limited knowledge and it does appear to test as bad.

I tested and am showing zero volts at both the breaker on the gen and on the switch panel in the boat. I don't know if that is good or bad sign for the cap being the issue.

I hope this is the only issue and the diodes are still good. -

I just received the shipping info and I should know the outcome sometime Thursday night. I will report back.
 
The Bill Collector said:
My Westerbeke has a hidden breaker switch on it. One weekend I popped it and that I was buying a new unit. Somebody told to look for the switch, found it, reset it and everything was great....
Click to expand...


Can you describe "hidden" a little better for me?

I have reset the main breaker on the gen, just below the manual start switches

I have reset the red breaker button below the fuse on the side of the control panel.

I have checked the fuse on the side of the control panel

I have checked the fuse inside the control panel

I have checked both breakers inside on the boat switch panel.

Am I missing one?
 
You found all the breakers and fuses.

I think it's just a bad capacitor and replacing it should solve the problem as what you described is certainly a bad can.

Darn. I though I had the right incantations to post photos here from my OwnCloud implementation. sigh Oh... right... I'm using a self-signed cert on that server. Oopsie
 
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mikenewhouse said:
... I know where they are, but think it is crazy that I would have to remove the whole metal backend to get to them. ...
Click to expand...

For me it was remove the whole back end, and I have a 12.5KW. I did try the cap and rectifier, however and they did nothing. I also ohm'd out the windings and they seemed good but no output. So it could only be the diodes. After I got to the diodes I decided to try and find a new back end just to be safe. It cost me $2500, but I got a whole newly rewound, rebuilt back end. Best thing I could have done. I did it last year around this time.

If you are planning on keeping this boat for a while, it might be worth the peace of mind going that route. Good luck!
 
SKybolt said:
For me it was remove the whole back end, and I have a 12.5KW. I did try the cap and rectifier, however and they did nothing. I also ohm'd out the windings and they seemed good but no output. So it could only be the diodes. After I got to the diodes I decided to try and find a new back end just to be safe. It cost me $2500, but I got a whole newly rewound, rebuilt back end. Best thing I could have done. I did it last year around this time.

If you are planning on keeping this boat for a while, it might be worth the peace of mind going that route. Good luck!
Click to expand...

Hope I don't have to go that far, Gen only has 400 or so hours on it, but it is 13+ years old so I am still hopeful it is just the cap.
 
mikenewhouse said:
Hope I don't have to go that far, Gen only has 400 or so hours on it, but it is 13+ years old so I am still hopeful it is just the cap.
Click to expand...

Hope it wors out for you. Gennie love to be beaten. 400 hours over 13 years is just over 30 hours per year. Not near enough to be exercised. If nothing DIY works for you, ther is a place near (?) LOTO that does all things W'beke. I'll have to find the name. Nice folks.
 
In Two Deep said:
There is a way to test the diodes. Westerbeke has troubleshooting guides for their products. Here is a link to one of them. You would need to find your model on the site and go from there.

http://www.westerbeke.com/Category/4.5BCGB/5399ADA2DAF73A26740BF65D#techdocs

Look for the "Electrical Troubleshooting Guide"
Click to expand...

Thanks for the link, I have all that downloaded. Again just can't get to the diode's yet - Would almost have to pull the genny to get the backend off.
 
My pleasure! Access is always an issue. My mechanic has to remove part of the starboard engine exhaust to get to the genny and then assign his smallest tech to the job. However they were able to replace my diodes last season without removing the penny it from the boat. I am sure they were calling me all kinds of names when they were in there :smt014
 
Re: Westerbeke Diode Replacement - Help - Fixed

THANK YOU to everyone and their replies - My Gen is Fixed.

Replaced the Cap and we are back up and running. I ordered and have the Diodes in case we need them someday but not today :) :smt038:smt038:smt038:smt038:smt038:smt038

Review for others:

Gen was running fine - Midday all power output stopped at once, it was not gradual.

Showing zero volts on both gauges in the boat - This was confusing because many post mention 60 or 80 volts points to your cap.

Replaced cap after checking all fuses and breakers - Fixed.
 
Re: Westerbeke Diode Replacement - Help - Fixed

mikenewhouse said:
THANK YOU to everyone and their replies - My Gen is Fixed.

Replaced the Cap and we are back up and running. I ordered and have the Diodes in case we need them someday but not today :) :smt038:smt038:smt038:smt038:smt038:smt038

Review for others:

Gen was running fine - Midday all power output stopped at once, it was not gradual.

Showing zero volts on both gauges in the boat - This was confusing because many post mention 60 or 80 volts points to your cap.

Replaced cap after checking all fuses and breakers - Fixed.
Click to expand...

Great news! Looks like I'll be replacing the cap. Where did you order it from?
 
mikenewhouse said:
I ordered directly from Westerbeke (they were the cheapest believe it or not).

http://westerbeke.com

35978CAPACITOREA$66.70
Click to expand...


The exact same thing just happened to me 2 days ago. We were transiting the Welland Canal in 90+ heat, and it was running great (providing much A/C relief between locks). Then it just stopped generating AC power - dead zero amps, but the engine running fine.

I'm ready to try changing the cap - I have the 7.2 BCGTC (carb version - 1999) which I'll bet is pretty close if not identical to yours. It's not clear from the documentation on how to access it. Is it just as simple as taking off the cover of the Back End? Or do I need to take off the control panel and/or remove any other parts like the stator or the entire back end? How difficult was it? I'm reasonably mechanical.

Any help you can offer is much appreciated.

Thanks
Dave
 
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