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Old 24-06-2012, 03:25   #1
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Alternator Keeps Dying

My alt died the other week and mechanic came and took it off and said the regulator was bad. He said he couldn't find the original regulator so the modified another one onto it to work.

When we tried it after the install we had to bring the revs up to around 20k then saw the charge on the dash instrument. Then when put the gas back down to idle or normal cruising revs 15k. It would still show it was out putting something. He said maybe just my engine didn't spin fast enough or something for it to kick in.

I left a few days later and when we where cruising on the engine I again had to bring it up to a higher rev then back down but then I also notice the gauge jumping around a lot. A few days later to the next port (current port) there was no out put from the alt any more. I think its dead again.

I had similar issues with it originally when it died. A mechanic will again be here to look at it in the next few days but if any one can give me any input on if its something with just he regulator on the alt or something deeper wrong with the alt please let me know.

Somethings I noted where when I start the engine (Mercedes OM-636) I hear a bit a of a whining sound appearing to come from the alt for about 5-8 secs.

Also when the mechanic reinstalled the alt he bypassed the sterling charger and said I didn't really need it it didnt do much.

The alt is connected to a battery isolator with that charges the starter batter (110ah) bank 1 (240ah) bank2 (460ah)

Please let me know any advice or suggestions. Thanks
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Old 24-06-2012, 03:50   #2
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Re: Alternator keeps dyeing

Sorry my friend but your 'mechanic' is a tad misleading. Firstly the noise from the alternator is one of three things, incorrect tension on the drive belt, bearings or brushes. If the alternator originally worked fine then the pulley ratio is OK. The OM 636 Merc engine had a Bosch alternator as standard and it's output should be 25% of your total battery capacity, Sterling should have told you this when you purchased it. My advice is to take off the alternator yourself, find a Bosch dealer and get a service exchange alternator of the correct capacity refit it with a new drive belt. A point to note, some alternator controllers have an extra wire fitted to by-pass the in built regulator, make sure you get a spark to refit this to your alternator or your Sterling won't work. personally I find the Adverc control system very reliable. I hope this helps you.
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Old 25-06-2012, 05:08   #3
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Re: Alternator Keeps Dying

so the alt should be putting out 200A ?
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Old 25-06-2012, 06:42   #4
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Re: Alternator Keeps Dying

I am not sure on how well it worked I only recently purchased the boat and the alt failed a few weeks after. The Sterling charger also was pre installed on the boat at purchase.

I added 460ah of batteries though after I purchased it and not sure if that did something to it.

If the Alt is not my main source for charging do I need 200a alt or is normal one ok?

The belt is new but it was making the noise before the new belt.

Is there way to calculate the ratio even though the pulley looks like its as old as the engine.
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Old 25-06-2012, 08:36   #5
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Re: Alternator Keeps Dying

Cruising revs are 15k?? thats 15,000 RPM???? Seems awfully high. Or is this some sort of speedboat?

So, what is the test you are using to conclude there is "was no out put from the alt any more".

If you are testing voltage then that isolator, spread across three banks of wide ranging sizes (110, 240, 460) may be fooling the regulator to shutdown (reduce the charge voltage).

A quick diagnostic test would be to bypass the isolator and connect the alternator output & reg directly to the largest bank.

But again, you need a reliable means of determining what is "really happening", ideally at each of the batteries. A dashboard light (probably measuring voltage) connected across the isolator that is paralleling three different size batteries will give you an incorrect, if not incomplete picture.
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Old 25-06-2012, 09:34   #6
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Re: Alternator Keeps Dying

Westsail42 - I saw that too. 20,000 revolutions per minute and 15,000 revolutions per minute at cruise - must be a gas-turbine (jet) engine as those are typical rpm's.

It is not difficult to attach an induction ammeter to the alternator output cable and read if there is any current in it.

And as mentioned by others, the mechanic is either smoking some funny stuff or doesn't know much about alternators. And with an external alternator regulator you need to attach the voltage sensing wire to the battery bank you want the alternator to take care of first.

If the alternator is "dying" - (what do you mean by "dying?") that usually means the alternator diodes have failed or the regulator has failed. A lot of times this is caused by insufficient or intermittent grounding of the alternator. Just relying upon the engine alternator mounting bolts to provide a ground is risky. A separate large ground wire is recommended between the alternator casing (ground terminal) and the engine block.
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Old 25-06-2012, 09:42   #7
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Re: Alternator Keeps Dying

Sorry about that I mean 1500 RPM.

A mechanic came over today and looked at it apparently the last mechanic hooked up some of the wires wrong. So he redid them and then also told me that the alt light led wire came out which is why it wasn't charging. He also recommended I put a different gauge wire from the amp meter going to the battery since it was too small.

I asked about the Sterling charger but he didnt really know how to test it or again to hook it up or not so he just disconnected it and said he knew they worked good when they worked but didnt know about the one I have.

There is a phone number on it and I tried to call them but seems its no longer in service. Theres no model really on it I have attached a photo.
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Old 25-06-2012, 10:03   #8
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Re: Alternator Keeps Dying

As the above 2 posts have pointed out there's obviously something radically wrong with the setup. I pointed out that the modern 4 step alternator charge controllers output are dependant on ALL the factors are usually recommended to be 20 to 25 % of the total battery capacity, this is to make the charging time as efficient as possible(particularly for sailboats) as well as boosting the battery's efficiency, i.e hold more charge.. I think a wise move would be to get all the details written down exactly, drop a nought of the revs, send an e mail to Sterling(with serial no of controller) with all the details and ask for a schematic diagram and their specifications.This must have been supplied by them already so ask the previous owner if possible. Then start at the very beginning, assume nothing, double check everything and take it step by step, if you find the task too daunting look around for an experienced auto/agricultural electrician. Not ALL, but many so called marine engineers are just that, so called.. Agricultural engineers are usually more versatile so don't rule them out, for instance your OM 636 engine was fitted to some combine harvesters and fridge units on trucks so they may even have spares on the shelf. If you have trouble getting spares for the OM 636 contact me and I'll put you in touch.
I hope this helps.
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Old 25-06-2012, 10:09   #9
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Re: Alternator Keeps Dying

Deepthought, here's Sterlings email add for you...Sterling Power Products: Manufacturers of High Quality Advanced Marine and Automotive Digital Power Products
I hope this helps.
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