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Old 23-05-2017, 20:11   #1
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Volt drop on Yanmar ign output.....

Owing to being made aware of this common Yanmar harness malady I am thinking of using a relay to supply decent battery voltage to field of alternator.
(Via MG smart charge one, max current 8A)
Anybody done this?
Easier whilst I'm setting this up.
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Old 23-05-2017, 21:27   #2
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Re: Volt drop on Yanmar ign output.....

Thats a little confusing.. If you put bat volts to the field you would get 50 volts or something. The field gets only 2-4 volts maybe.
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Old 23-05-2017, 21:32   #3
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Re: Volt drop on Yanmar ign output.....

another device to go wrong. The key is good, sealed connections and ample wire diameter.
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Old 23-05-2017, 22:24   #4
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Re: Volt drop on Yanmar ign output.....

Quote:
Originally Posted by Guy View Post
Thats a little confusing.. If you put bat volts to the field you would get 50 volts or something. The field gets only 2-4 volts maybe.
Supplying smart charger 12.xV which supplies field at
whatever.

Currently (haha) start solenoid is taking multiple presses to get starter to turn over. Figger its already got bad connections via ign switch.
All other connections are new and over capacity.
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Old 23-05-2017, 22:26   #5
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Re: Volt drop on Yanmar ign output.....

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another device to go wrong. The key is good, sealed connections and ample wire diameter.
I agree. Just want to nail this hi output alternator install.
Last one was dismal.
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Old 24-05-2017, 08:50   #6
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Re: Volt drop on Yanmar ign output.....

We had a monster thread on this not long ago! Will find the link ;-)

I'm heading back to boat next Monday and that is top of my list. Going to go the larger guage route I think.

We'll see.
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Old 24-05-2017, 08:56   #7
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Re: Volt drop on Yanmar ign output.....

Here is the start of that thread, I'm not sure how to copy a link :-)

Yanmar occasionally won't start, then does.

Symptoms. Yanmar 4j series starts 90% one turn of the key. 10% turn key, nada.



Wait a sec, turn....turn.....vroom. (May be one extra turn or up to three but does start.



Disconcerting.



Fresh start battery, new starter and solenoid last year (swapped out old one just to be safe and that solenoid checked out good)



Replaces Yanmar ignition switch which seemed to help.



On old boat we had similar issue and I recall installing secondary relays as the voltage drop to the solenoid was thought to be to great and that solved.



Anyone have similar issue??????



Side note, we're in Bimini! Say hello :-)

Yanmar occasionally won't start, then does. - Cruisers & Sailing Forums
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Old 24-05-2017, 14:22   #8
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Re: Volt drop on Yanmar ign output.....

Thanks for that. Reread.
Still, unsure whether the voltage drop will impact charging.
Going to hookup w/o relay and check numbers.
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Old 25-05-2017, 04:17   #9
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Re: Volt drop on Yanmar ign output.....

The voltage drop typically only impacts the starter solenoid which is relatively high current. A typical internally regulated alternator needs minimal current to start charging. Once it gets going it self-excites.
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Old 25-05-2017, 04:47   #10
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Re: Volt drop on Yanmar ign output.....

Quote:
Originally Posted by lateral View Post
I agree. Just want to nail this hi output alternator install.
Last one was dismal.
What Yanmar engine?

What alternator?

The wiring problem you appear to be referring to does not affect the alternator which in the stock alternator, is internally regulated and gets it's sense voltage direct from the output wire which does not go anywhere near the on/off/start switch wiring.

If you have a non stock alternator, it will probably be externally regulated and so again will not be affected by this problem.
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Old 25-05-2017, 04:52   #11
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Re: Volt drop on Yanmar ign output.....

Quote:
Originally Posted by lateral View Post
Owing to being made aware of this common Yanmar harness malady I am thinking of using a relay to supply decent battery voltage to field of alternator.
(Via MG smart charge one, max current 8A)
Anybody done this?
Easier whilst I'm setting this up.
There are two kinds of Yanmar owners --

Those who have installed starter relays
Those who will install starter relays after they get sick of starting problems . . .


I am in the first group.

I had difficulty identifying the problem and wasted a lot of time suspecting the starter itself, other aspects of the wiring

Once I figured it out, 30 minutes with a crimper, Molex connectors, spare wire, and a car relay I had on board solved the problem once and for all
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Old 25-05-2017, 04:54   #12
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Re: Volt drop on Yanmar ign output.....

Quote:
Originally Posted by boatbod View Post
The voltage drop typically only impacts the starter solenoid which is relatively high current. A typical internally regulated alternator needs minimal current to start charging. Once it gets going it self-excites.
On my installation, there is a relay for exciting the secondary (school bus) alternator plus unlocking windlass and bowthruster and turning on engine room blowers. I had a good deal of trouble with this as well, solved only by replacing some of the wiring, remaking connectors, replacing the relay.

Yanmar wiring pretty much sucks in my opinion.
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Old 25-05-2017, 12:46   #13
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Re: Volt drop on Yanmar ign output.....

Quote:
Originally Posted by Dockhead View Post
There are two kinds of Yanmar owners --

Those who have installed starter relays
Those who will install starter relays after they get sick of starting problems . . .


I am in the first group.

I had difficulty identifying the problem and wasted a lot of time suspecting the starter itself, other aspects of the wiring

Once I figured it out, 30 minutes with a crimper, Molex connectors, spare wire, and a car relay I had on board solved the problem once and for all
Yep.Dumb to procrastinate when its easy.
Pushing the button multiple times with a pained expression on my face.
Thinking, One day this won't start at all.
All & sundry thinking- what up with your battery- you going out with that?
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Old 25-05-2017, 12:56   #14
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Re: Volt drop on Yanmar ign output.....

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Originally Posted by Wotname View Post
What Yanmar engine?

What alternator?

The wiring problem you appear to be referring to does not affect the alternator which in the stock alternator, is internally regulated and gets it's sense voltage direct from the output wire which does not go anywhere near the on/off/start switch wiring.

If you have a non stock alternator, it will probably be externally regulated and so again will not be affected by this problem.
Yanmar 3gm30f
Bosch 120A 0 120 458 034 ---Hitachi 55A is backup. (Stowed)
Externally regulated by a Mark Grasser Smartcharge one.
The yellow feed wire goes from ignition to ext reg and must be able to carry 12v- 8A.
The ext reg then adjusts the output voltage from the stator via adjusting the field voltage. (Or current, or both via adj voltage?)
I'm going to try without and see how it works.
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Old 25-05-2017, 13:08   #15
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Re: Volt drop on Yanmar ign output.....

Quote:
Originally Posted by boatbod View Post
The voltage drop typically only impacts the starter solenoid which is relatively high current. A typical internally regulated alternator needs minimal current to start charging. Once it gets going it self-excites.
Yep, thanks. But it is externally regulated and I'm not sure how the 12v powered ext reg will handle the volt drop.

Brain phart a minute ago.
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