nighthawk 550 electrical problem

Thanks for the information. I have checked the voltage of the batter
when started and the voltage goes from 11.45 to 11.85 volts while yo
rev the engine. The battery voltage before I put it in the bike i
12.85. It does not take long for it to drop below 12volts. My questio
to you before I start attempting to test the diodes in the rectifier i
should I wait until my Clymer manual gets here later this week to loo
at the schematics? I am really not sure which wire is what otherwise
Also, while the bike is warming up it seems like the right bank o
cyclinders are missing until the bike is warmed up. By then you migh
be able to ride for 15mins or so before the battery loses enoug
voltage for the engine to shut off or run horribly. Going through som
of the Electrosport flow chart for troubleshooting the charging syste
points to the problem of a loose ground. I have removed the tank an
checked the ground under there as well as the ground attached to th
engine crankcase. There is also a ground that bolts to the frame nea
the battery and it is ok too. The flow chart said to jump a ground fro
the neg terminal on the battery directly to the ground wire on th
rectifier and that does not seem to help. Also I have checked th
connections to the rectifier and they are tight and clean

 

If you can, feel the stator of the alternator after running the bike at
about 3000 rpm for a minute. If the rectifier is bad that stator will
generally be really hot! He careful as I have seen car alternators get so
hot as to cause water drops on the cover to sizzle and dance.

Given that it is trying to charge, I would say that one or more rectifier
diodes are bad. Just keep in mind that a diode is nothing more than an
electrical "check valve". It is supposed to allow current to flow one way
only. If it doesn't it is NFG.

pierce

 

jlpridge wrote:

That suggests a number of unpleasant possibilities. You may have an
open or shorted stator, really bad electrical connections or a shorted
battery cell, or the SCR or zener diode inside the RR unit are shorted
out.

Your alternator does not have a lot of power, maybe only 300 watts. If
you run the open circuit test I mentioned, you'll get around 90 to 120
volts between any pair of AC output wires.

But, even if the open circuit test proves the stator is OK, it still
doesn't have enough power to raise its own voltage much above the
battery voltage if there is a heavy load on the alternator, like a
shorted battery cell, a grounded SCR, or if there are blown diodes in
the rectifier.

You don't have an owner's manual with a wiring diagram in the back?

If you follow the wire harness from the alternator to the rectifier, it
will go to one connector on the RR unit. That connector will probably
have three wires going into it, so those three wires will have three
pins in the connector. With a 3 phase alternator like your Honda has,
you can't go wrong on which AC input pin you stick your probe to on the
RR...

The other connector probably has two wires going to it. If it has three
wires, one of them is probably a sensor wire. Honda is the only company
I know of that runs a voltage sensing wire off to someplace else in the
instrument panel or headlight.

But, from looking at the DC output connector, you should easily be able
to figure out which is the DC positive output wire. It will be the same
color as the small wire going directly to the battery. It's probably
RED.

The DC negative output wire could be green or black. It's easy to tell
which is the DC output wire. If you probe it with the ohmmeter on the
RX1 scale, it should be grounded to the fame, so you'd get zero ohms
between the connector and the engine.

But all the above is to help you identify the pins on the RR unit
itself. That's what you want to be testing when you do the diode test.

That could be caused by dirty idle jets in the carburetors or you might
have some really bad electrical connectore. If the electrical
connectors in your wiring harness have dirty corroded pins that have
turned green, or even worse, have turned black and the plastic
connectors have begun to melt, the alternator can't charge the battery,
the electricity gets used up heating the connectors.

Every electrical connector will get hot, due to resistance. The more
connections you have, the more charging current is wasted in heating
those extra connections.

The Suzuki engineers did a number of strange things on my GS-1100 that
made it very hard to keep the battery charged.

One problem was that they used the stator and rectifier plugs that came
from the supplier. The stator wouldn't just plug directly into the
rectifier, the plug was wrong. So Suzuki made a short pigtail harness
that attached the stator to the wire harness and the rectifier plugged
into the pigtail harness too. That doubled the number of connections in
the charging circuit that could get hot and melt.

Suzuki also ran one wire from the stator up into the headlight shell to
a connector that had once gone to the headlight ON/OFF switch. Their
idea was that you didn't need all the output from the stator if the
headlight wasn't turned on...

Disconnecting one of the three stator leads in a three phase alternator
such as your Honda and my Suzuki have cuts the stator output in half.

But there hasn't been an ON/OFF switch on the handlebars for years.
Motorcycles sold in the USA must have their headlight on all the time.

So the Suzuki engineers put a jumper wire in the connector inside the
headlight shell so the electricity could travel all the way back to the
rectifier unit. And that little jumper wire got hot and it melted the
connector and kept that phase of the stator from charging my battery.

I was buying a new battery every year until I figured out that I needed
to cut off all the burned up coonnectors and solder the wires directly
together.

Honda owners have also been busy tracking down all the excess
connections in their charging circuits, cutting the connectors off,
stripping the wires, twisting them together and SOLDERING them together
to eliminate all the high resistance connections.

 

I'm not sure what you can tell about a charging system from the fact
that the parts get hot, except that it's not a good idea to touch hot
parts.

There is always some heating in the metal cores because of molecular
friction as the electric currents try to align all the iron molecules
to a north-south axis. That's what engineers call "iron loss".

There is always *some* heating in the copper windings, if current is
flowing at all. Electrical engineers call it I-squared R loss, or
"copper loss".

If you are carrying a 300 watt load on the alternator at 12 volts,
Power/Volts = Amps, so 300/12 = 25 and since the internal resistance of
the stator may be as high as 1 ohm, 25 X 25 X 1 = 125 watts. You know
you can't put your hand on a lit 125 watt light bulb, so a stator with
125 watts
I-squared R loss is going to be noticeably hot to the touch...

This particular Honda's alternator does have a cooling fan, but the
internal temperature rise might be as much as 180 degrees Celsius.
Since the windings have nothing for insulation except some special
enamel, the solvents in that enamel will begin to boil out and that
distinctive odor of a hot electrical transformer will be noticed.

And, some of the heating you may have noticed in a car alternator may
be due to at least two other sources. One of those sources is the six
diodes that are built into the case. A diode is a semiconductor with
gawd only knows exactly what low resistance in the forward direction
and (hopefully) quite a bit more in the reverse direction.

Since current flows through the diode, the I-squared R effect makes it
get hot.

If the diode is conducting equally in both directions, it just gets
hot, and doesn't rectify AC into DC. I couldn't tell you what the
forward and reverse resistances are of any particular diode, because
the battery in an analog ohmmeter biases the diode and changes the
reading. If a shop manual specifies a resistance reading for a diode
test, it probably also specifies what model of ohmmeter to use.

The other potential source of heat in a car type excited field
alternator would be the rotor. If the diodes are bad, or the battery is
low, or there's a heavy electrical load the car's voltage regulator
will send full current to the rotor and the I-squared R effect will
cause massive heating of the rotor.

In a motorbike's permanent magnet alternator system, the diodes are in
the rectifier regulator, so the heat sink of the RR gets hot, whether
the diodes are working right or not. And, the voltage regulating
components inside also get hot, the zener diode and the silicon control
rectifier both have internal resistance and the SCR is expected to get
hot, it's a semiconductor and I-squared R effect is busily making it
hotter than hell.

Ah, yes. NFG means "not functionally good" of course...

 

Why yes it does! (;>)