Yanmar Engine control panel light

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Scotian

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Jun 8, 2004
39
CS 27 - Nova Scotia (Pugwash)
Did a moonlight sail Friday and while motoring after dark (first time) noted that one of the two diesel warning lights had a slight glow. It was the one on the left and am assuming it is the alternator light. It was so dim, one would never note it during the day.

Appreciate any comments re situation and if it indicates a problem that one should address..
Thanks
 
W

waternwaves

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Feb 6, 2009
257
Hunter 40 Camano Island
First guess would be low voltage at the panel,

Would check in the following order with an accurate Digital volt meter

1) At the alternator terminals,2) Lighter terminal on cabin control panel, 3) Starter battery contacts. Lastly 4) the alt sense circuirt at the helm panel.
Also vary the engine speed to see if the light goes out


the reason you want to check output varying with engine speed is because I have had a single failed diode which still allowed the light to go when engine RPM was over 2900 rpm.

YMMV
enjoy.
 
sailaway78

sailaway78

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May 11, 2005
3,431
Seidelman S37 Slidell, La.
Alternator

If the light is just barely glowing, probably you have a diode in the alternator burned out. Have the alternator checked at a good alternator shop. Had this same thing just recently, after a lightning strike. The way it works is the light is grounded through the regulator with the key on and the engine not running.. When the alternator is charging, the voltage is the same on both sides of the regulator and the light goes out. Not many things there to cause this problem. It is possible you have a bad connection, but more than likely it's a bad diode.
 
A

alexco38

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Sep 25, 2008
1,096
CS 30 Toronto
Nothing wrong. The dim glow is part of the charging circuit. The field coil need a small current to go thru in order to excite the generation of current. If the light is burnt out, the alternator will not generate any current.

Just google how alternator work and you'll get the answer.
 
Bill Roosa

Bill Roosa

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Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
Nice and easy's explination is correct, the light should go out when the alternator is charging and come on when it is not. If it is on there is some sort (probably minor in this case) of problem. A bad diode fits the sysptoms as does insulation on the wire between the alternator and lamp going bad and leaking through a high resistance. While checking the diodes check the wire for chaffing.
 
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