Charging lamp

[Galini]

I would appreciate some advice from one of you gurus who knows about electrics.
The charging lamp on my diesel glows brighter as the revs increase, instead of going out to show that the charging circuit is fine. This is only a new phenomenon. The ammeter still registers positive. According to my meagre knowledge these events are contradictory.
Any advice would be appreciated.

Gary
Galini

[Dolphin]

G'Day Gary,
You may have a problem with the main wire leading from the Alternator to the battery switch.
With the battery switch off, look along the length of the wire for loose or corroded connections. Just wiggle the joints to see if they're firm. Do this when the engine is OFF as you may break a wire and open circuiting the alternator will blow up the main diodes in the alternator due to high open circuit voltages.
If you run the engine at high revs for a while and then feel the joints along the wire you may find one that is hot and thus indicating a high resistance or bad joint. I don't know the circuit on the Sole but if it is a basic one the earth wire on the motor should be checked too in the same way.
If you have a multimeter measure from the B+ wire, which is the big terminal on the back of the alternator, to ground and that should be 13.8 to 14.2 volts or so. If it is, then you can pretty well cancel out any problems with the alternator. Another clue to an alternator problem is if there is a lot of alternator whine on your radios.
Next, with the engine idling, measure the voltage drop along the main cable by connecting the multimeter to the B+ terminal (Positive or red lead of the meter). And to the Common on the battery switch, (negative or black lead of the multimeter). As you rev the engine the voltage should increase and this voltage is the one that is making the light glow. It should be less than a volt and go up and down and correspond with the ammeter.
Other than that I can't think of anything else that I can help you with without actually seeing the boat.
The other thing to remember is that the alternator is voltage regulated and it will pump as much current into the batttery until it reaches 14 volts and stop increasing despite how many engine revs you give it. If you've done a lot of cranking to get it started it may not be able to supply enough current to get the battery voltage to 14V for a while, particularly at idle.
The charging light is connected from the common on the battery switch, through the ignition switch to the D+ terminal on the alternator. That is usually a 6mm wide flat terminal (Spade) on the back of the alternator. The D+ terminal is connected as a copy of the B+ terminal using 3 small diodes. So both these voltages should be the same. The light is connected between the two to indicate if something is different and thus indicating an alternator fault.
The charging light is important in that it supplies some current to the alternator field, the rotor, to start the alternator charging at lower revs. Otherwise I would have just said remove the light and there is no more problem ;-0)
I hope it helps

Greg
Felicite.

[Galini]

Thanks, Greg. That is a fully comprehensive description. Great work.
Regards,
Gary
Galini