Regulator and driving lights

 I recently installed a set of 30 watt driving lights to my KLR 650. At
the same time I upgraded the headlight loom to eliminate a severe
voltage drop at the headlights. I did a ling ride (1000k) with the
headlights on low beam all of the time except for a two hour night
drive with high/low beam and driving light combinations as needed.
Everything operated very well.
A few days later I went for a short drive to tweak the headlight
alignment. Finished that, and turned for home,put all lights on and
all went dead!
Bugger!
The engine kept going so I stopped it, and after a bit of fumbling in
the dark, found the culprit, a blown main fuse in the regulator to
battery line.
This fuse then started to blow regularly about 5 minutes after I added
the driving lights to high beam.
I've checked everything and can find no dead shorts. My multi meter
says that the load on this line with engine stopped and all lights on
is about 10 amps. This consists of tail and instrument lights and
relays for the head and driving lights, and the intermittent maximums
for brake and turning indicators. The driving current for these is
from a different circuit. This seems about right, although I wonder
whether this line should be taking this load at all, as there is a
separate fuse for the headlight controllers.
When the engine starts and revs to about 3000, the multi meter
readings reverse and show charging current. This sits around 15 amps
with all lights on except for the driving lights. When I turn on the
driving lights, the amperage increases slightly, then stabilises for
about 3 minutes, the goes through the roof - amps outside the range of
the multi meter, and the main fuse blows.
I blew the fuse in the multi meter so I haven't been able to get a
voltage reading but I'm betting this would be through the roof too.
The local auto-electricians have only recently come down from the
trees so I'm forced to deal with this problem myself. My question is,
is the increased load somehow influencing the voltage regulator and
causing it to lose control, or is the voltage regulator just toast?
What tests do I need to do to confirm this?

--
Sam

 
sam...@hihat.com wrote:

All the voltage regulator does is shunt excess current to ground
through one silicon control rectifier that comes off on one of the
diode pairs in the 3-phase full wave rectifier bridge...

The SCR is hooked up between the anode of one diode and the cathode of
the other diode in that pair...

The zener diode senses voltage off the same point that the SCR is
hooked to. The current through the zener is reduced by a resistor...

When the zener diode reaches its avalanche point where it conducts
current, it triggers the gate of the SCR and grounds out that one phase
of the alternator. But, since the 3-phase alternator is wye wound,
current on the postive alternation from one phase has to return to a
different phase. The end result of grounding out that one phase is that
the alternator's output is cut in half, not just by 1/3rd as would seem
to be the case from a cursory examination of the circuit diagram....

In a permanent magnet alternator system that is connected to a battety
through a rectifier bridge, the battery stabilizes the system. Though
the alternator stator would put out around 100 volts if the plug from
the RR unit was disconnected, the voltage across the battery will be
reduced to 11 to 15 volts with the battery connected...

If you measure across a fully charged battery with the engine running
and all the headlights off, you should see the voltage rise from
12.something volts to about 14.5 to 15.0 volts and then sharply drop
off as you raise the engine RPM...

When you reduce the RPM, the voltage should drop back to around
12.something and when you increase the RPM again, the SCR will ground
out that phase again and the voltage will drop, and you can repeat that
cycle until you get tired of it, the RR is going to do that all day...

If you rev up the engine and the voltage across the battery stays below
12.7 volts or so with a fully charged battery, you can suspect many
problems in the system. Stator problems, wiring, blown diodes in the RR
are possibilities...

If you rev the engine up and the voltage goes *down* you may have a
short circuit in the battery or in the wiring somewhere...

The fact that you can run your lights for five minutes before the
fuse blows indicate an intermittent short in the wiring somewhere...

Also, examine the plug on your RR unit carefully. Are the pins
blackened and discolored? Is the plastic melted? That's a sign of a
poor electrical connection...

 On 14 Apr 2005 10:31:53 -0700,  krusty kritter wrote:


Thanks for that. I will print and file it for future reference - it's
one of the best explanations I've seen.
I've put the bike together and had a 20 minute run, no problems, just
lots of light. Wonderful!

--
Sam

 On 15 Apr 2005 09:51:02 -0700,  krusty kritter wrote:

[.. excellent info]

It's a known issue, and you can jumper it so that it's reversible if
you want to sell the bike (I don't). Yes, it's been done.


Heh - yes and a screwdriver and spanner to dismantle the stupid bike
to get at the fuses - BTDT. That's the next project - an accessible
fuse box.

--
Sam