First of I supose I should mention I think car batterys are about 11.5-7v,
don't know why they go over 12 volts but put a load on it for a couple of
minuets and it should go down.
If your altinator shreeks, tighten your fan belt or suspect fault bearings.
Supose I might need to say what the bulb actualy does.
I'll start with starting (bootstrap).
You turn on the ignition, the ingition warning light is atached from battery
+ to field coil +, current (conventional) flows through the bulb to the
filed coil. A magnetic field is then generated. The voltage at the field
coil + is somewhere between battery + voltage and battery - voltage(0) (see
potential devider theory). Anyway this is enough for the altinator to
bootstrap.
The main coils start generating a voltage, which is regulated and a copy of
the battery charge voltage is given to the feald coils.
There are TWO connections to the battery + one thick which charges the
battery, and supplys the power from the altinator to the car, the other is
the sence which is employsed in a "negative feedback" type regulating
system. It looks at the battery terminal voltage and tryed to maintain it
at 13.5-14.5 volts.
This is where you should hopfully see a theory for the dim light.
Now take a look at power output line, this has alot of current going through
it, it will experience a voltage drop accross it. Thus the terminal voltage
goes down, the altinator bumps up the output voltage to take the battery
voltage to 14.5 volts.
So we have this situation assuming the altinator is set to maintain 14.5v
there is a 1 volt drop on the power line, the sence reads 13.5 volts at the
battery, the altinator increeses the power output (and the filed coil
volage) to 15.5volts, thus the battery is still beeing charged at 14.5volts,
but the field coil is at 15.5 volts.
Given that the field coil is connected to battery + via the warning light
you have a 1 volt difference, this will be enough to light your warning
lamp.
So how can you stop this? The most likly suspect is the connectors on the
altinator or even the power wire. Clean these up prefrebly renew with new
higher rated wire and you should cure the problem.
You will also notice as the load goes up the voltage gets higher and your
light get's brighter another reason why you see it more at night.
Havent lost anyone have I
James
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