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Old 19-11-2016, 15:10   #1
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Volvo penta alternator

I have a Beneteau 350 with a 2003 Volvo Penta. The battery voltage does not change when I start the engine, but I do not know if it is due to the regulator. How can I check this out without removing the alternator?
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Old 19-11-2016, 16:01   #2
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Re: Volvo penta alternator

Easiest test is to put a clamp on DC amp meter on the output wire from the alternator. Typically thats the big red wire attached to the alternator.

Do you know if it is internally or externally regulated?
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Old 19-11-2016, 17:02   #3
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Re: Volvo penta alternator

No, how do you figure that out?
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Old 20-11-2016, 05:27   #4
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Re: Volvo penta alternator

An internal regulator is mounted inside or on the alternator so connections from the regulator to alternator are internal and not typically visible. An external regulator is mounted remotely with wires connecting it to the alternator. The primary connection from the regulator to the alternator is the "field" wire.

Stock Volvo alternators are internally regulated. To be externally regulated they must be modified to by pass the internal regulator. The tell-tale sign of this is usually a small wire, the field wire, that runs directly into the case of the alternator. It does not attach to a stud like all the other wires on the back of the alternator.

The most common modes of failure for alternators are:

Blown Bridge Rectifier Diodes. Usually caused by the output of the alternator being deprived of a sink...like turning the battery master switch off while engine is running.

Failed Regulator. Heat, vibration, age take their toll.

If you want to learn more, then these failures are field diagnosable, but require removing the alternator, partial disassembly, and multimeter use.

If not, then test for output as originally suggested. If none or very low (note: test with engine at about 2,000 RPM for full alternator output...carefull of moving parts) then remove (or have a mechanic remove) the alternator and take it to an alternator shop for testing. Both the above common problems can be reapaired quickly and inexpensively. If it tests good, then the problem lies elsewhere.

Do you get normal readings at your tachometer when you rev the engine?
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Old 20-11-2016, 05:34   #5
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Re: Volvo penta alternator

Greetings and welcome aboard the CF, Sailhope.

Post 1 ➥ BASIC Alternator Testing
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Old 20-11-2016, 06:21   #6
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Re: Volvo penta alternator

Thanks for the reply, it is very educational. The tach stopped working years ago. I had the alternator tested and it was good, but they said the output signal to the tach was not working. I have used the boat this way for 6-8 years, setting rpms by ear. Now when I look at the replacement alternators, they only show three connections, not the four I have on the P/N 873770 alternator I have. Also, I don't understand why there are such differences in the prices of the replacements i.e 129$-566$.
Really appreciate your thoughts and help.
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Old 20-11-2016, 06:55   #7
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Re: Volvo penta alternator

Quite often alternators kick in only after you rev up.

So first thing is make sure you alt has kicked in (or not). You see this immediately from voltage over the start battery.

b.
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Old 20-11-2016, 11:05   #8
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Re: Volvo penta alternator

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Originally Posted by Sailhope2633 View Post
Thanks for the reply, it is very educational. The tach stopped working years ago. I had the alternator tested and it was good, but they said the output signal to the tach was not working. I have used the boat this way for 6-8 years, setting rpms by ear. Now when I look at the replacement alternators, they only show three connections, not the four I have on the P/N 873770 alternator I have. Also, I don't understand why there are such differences in the prices of the replacements i.e 129$-566$.
Really appreciate your thoughts and help.
So, its been charging OK for 6-8 years and just recently stopped right?

Alternators are prettty simple devices and in most case can be repaired inexpensivley, including tach output, if you take it directly to an alternator shop.

Anything branded as Volvo is stupid expensive, and nothing on your motor is actually built by Volvo. The alternator is not specific to your motor. So, if you want to buy a replacement, do not buy Volvo (thats probably the $566 alternator which is in fact exactly the same as the $129 alternator).
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Old 20-11-2016, 11:33   #9
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Re: Volvo penta alternator

Here is a labeled pic of the back of your model alternator which shows what each stud is used for. All alternators will have similar connections, though labeling of posts, position, and sometimes number of connections, may vary by manufacturer. Replacing with an alternator with the same connections will simplify the installation.

The yellow wire which connects to the B+ stud provides "battery sense" voltage to the regulator which the controls the alternator output.The regulator, whether internal or external, does this by applying voltage to the alternator "field". Increased field voltage = increased output. No field voltage = no output.

One way to test for a failed regulator is to directly apply voltage to the alternator field (very briefly!). If the alternator produces normal output then its good and the regulator is dead.

The internal regulator is behind the cover, with the fan like pattern on it, at the top of the alternator.
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Old 20-11-2016, 11:43   #10
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Re: Volvo penta alternator

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Originally Posted by GordMay View Post
Greetings and welcome aboard the CF, Sailhope.

Post 1 ➥ BASIC Alternator Testing
Good guide and discussion posted by Gordy.

Also as mentioned in the thread, Nigel Calder has a couple of excellent books which together cover almost every common boat sysyem, including alternators, in a very efficient style (you could write volumes on this stuff, but he does it in two medium sized books).
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Old 20-11-2016, 14:52   #11
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Re: Volvo penta alternator

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Originally Posted by belizesailor View Post
Here is a labeled pic of the back of your model alternator which shows what each stud is used for. All alternators will have similar connections, though labeling of posts, position, and sometimes number of connections, may vary by manufacturer. Replacing with an alternator with the same connections will simplify the installation.

The yellow wire which connects to the B+ stud provides "battery sense" voltage to the regulator which the controls the alternator output.The regulator, whether internal or external, does this by applying voltage to the alternator "field". Increased field voltage = increased output. No field voltage = no output.

One way to test for a failed regulator is to directly apply voltage to the alternator field (very briefly!). If the alternator produces normal output then its good and the regulator is dead.

The internal regulator is behind the cover, with the fan like pattern on it, at the top of the alternator.
Opps, forgot the link to the pic:

https://www.google.com/search?client...-o1tJ-ilDMM%3A
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