-===XJ-OWNERS Electrical System FAQ===-
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[Last modified June 23, 1998. © 1998, Aaron Berg]
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1. Introduction
2. Fuse Box
2.1 Replacing
3. Battery
3.1 Battery Health
3.2 Checking Your Battery
3.3 Battery Survival
3.4 Battery Sensor
4. Starter Solenoid
4.1 Checking The Solenoid
5. Starter Motor
6. Alternator/Regulator/Rectifier
6.1 Alternator Connections
6.2 Alternator Brushes
6.3 Regulator Box
6.3.1 Checking Diodes
7. Ignition
7.1 Coils
8. Headlamps, Lighting, Accessories
8.1 Upgrading
8.2 Good Idea?
8.3 Problems
8.4 Recommendations
8.5 Suggestions
8.6 The Little Driving Light
8.7 Headlight Relay
9. Computer Monitor System
10. Canceling Turn Signal
11. Overcharging (You've heard so much about it.)
11.1 Batteries Boiling
11.2 Solutions
12. Corrosion, Connectors, Rants
12.1 Fixing Corroded Connectors
12.2 The Next Best Way
12.3 Corroded Connectors Don't Always Look Corroded
12.4 Where Do I Start?
12.5 Editorial Comment On Connectors
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1. Introduction:
So you've got yourself an XJ bike, and it seems to be doing something
strange of an electrical nature. The early eighties were a great time
for motorcycles. Modern performance just coming into its own, more
power, better ergonomics, but still those really gorgeous air-cooled
engines, polished aluminum unfettered by stupid decal-laden GOOF-2
style fairings. And new, more complicated electrical systems, that
are just now starting to show their time induced weaknesses.
This document is meant to be a starting point for discussions about
the Electrical System of the 1980's Yamaha's XJ bikes. Although most
of the information applies to XJ650s and XJ750s, some is specific for
the Seca 750. Other information may pertain to motorcycles in
general. It is not meant to be a substitute for a good wiring diagram
and manual. I have tried to avoid many of the electrical myths that
seem to show up so commonly.
2. Fuse Box:
There are four fuses in the fuse box under the seat. The main fuse
(30 amp) connects the battery to the both the alternator output and
the bike's key switch (which feeds the other 3 fuses). The battery
charges through the main fuse while the bike is running, and feeds
the other fuses when the bike isn't. The other fuses, each 10 amp,
are for the headlight (and driving light), ignition, and signals
(turn signals, brake etc.) There is a fifth fuse, behind the
headlight that feeds the parking and dash lights.
2.1 Replacing:
The fuse box on these bikes sucks. It is the first thing you should
replace. It sucks because it uses glass barrel-style auto fuses and
exposed, crimped connectors which are all subject to corrosion. Since
it is connected directly into the wiring harness, periodically
installing new connectors can leave you without enough wire.
Replace each of the four fuses with in-line ATC Blade type fuse
holders and fuses. Solder, seal and shrink wrap these into the
harness, there is plenty of room under the seat for them. Don't use
multiple fuse blocks, the in-line holders are better protected from
the elements and less prone to corrosion. Mark each fuse with
permanent ink, and add a few nylon wire ties, and you're in business.
A corroded original fuse block is notorious for causing intermittent
problems brought on by vibration. Things like ignition cut out, total
power failure, loss of headlights, and stalling at idle are examples.
3. Battery:
The standard battery (most models) is a Yuasa Yumicron YB14L-A2 12
volt lead acid/antimony battery. It is rated for 14 ampere-hours (at
10 hour discharge rate), and 190 cold-cranking amps. 14 AH
(ampere-hours) is a measure of the battery's capacity, and 190 CCA
(cold-cranking amps) is a measure of how much current the battery can
supply to the starter when it is cold out. (See www.yuasabatteries.com
for lots of useful battery info.)
Yuasa also makes one of its GRT (Gas recombination technology)
batteries that will fit the bike, although it is not clear that
Yamaha's battery sensor system is compatible (it can easily be
bypassed.) A catalyst material is used to recombine the battery
gasses so that the periodic addition of distilled water is
unnecessary.
*[Bypassing the sensor is a simple as connecting the sensor wire to
the positive terminal on the battery.]*
Lead-acid batteries contain both lead and sulfuric acid. The lead is
dangerous to the environment. That is the reason old batteries should
be disposed of properly. The acid is dangerous to clothing, hands,
paint, etc., but can be neutralized easily with baking soda or lime.
For people interested in the chemistry,
Pb (s) + PbO2 (s) + 2 H2SO4 (35%aq) --> 2 PbSO4 (s) + 2 H2O (l)
is a representation of the primary chemical reaction inside the
battery during discharge. As the battery discharges, lead, lead oxide
and sulfuric acid are converted into lead sulfate and water. This is,
of course, more than you wanted to know.
3.1 Battery Health:
A strong battery is required to keep your bike in good running shape.
A bad battery can:
--Make it difficult to start the bike. While it could have enough
juice to turn the starter, the voltage might drop so low, the
electronic ignition will not spark well or at all.
--Draw too much current from the alternator while running. This may
cause spark problems and possibly do bad things to the alternator or
the regulator.
--Cause stalling at idle. The battery may not have enough reserve
power to keep the ignition and lighting going when the alternator is
moving slowly.
3.2 Check your battery:
A battery hydrometer can be purchased in an auto parts store, it is
used to measure the state of charge of the battery. It basically
measures the amount of sulfuric acid in solution by specific gravity
(the "density" of the electrolyte). They come with instructions.
Standard batteries are fully charged at 1.265 specific gravity.
Yuasa's YuMicron, and other batteries with sulfate stop additives are
fully charged at 1.280. (The sulfate stop additive, included in
YuMicron batteries, increases battery life by reducing sulfation.)
You can also load test the battery, although an automotive load
tester is likely to draw too much current for an accurate test, it
can be used to give you an idea of the battery's condition. A more
accurate test is to measure battery voltage during cranking. Simply
apply your voltmeter to the battery and turn over the motor with the
"engine off" switch engaged. Battery voltage shouldn't drop below 9
or so volts while the starter is going.
3.3 Battery Survival:
There are several things you can do to keep your battery in good
shape for a long time. The life-time of a lead-acid battery is about
5-10 years, although automotive manufacturers tend to warrantee them
for less time. The die early from: Deep discharges, overcharging,
electrolyte contamination, and loss of electrolyte.
When you buy your battery: Be sure to fully charge the battery
before first use. Simply filling with electrolyte only brings the
battery to about 80% charge. If you use the battery before fully
charging it, you will damage it permanently. Unscrupulous motorcycle
dealerships don't think this is a big deal. I do, and so does Yuasa.
1.5 amps for three or four hours should do it.
During the season: Keep an eye on the charging voltage and
electrolyte level of your battery. Watch for overcharging: See the
section on "batteries boiling" for details. Always use distilled
water when adding to the electrolyte; do not overfill. Be sure the
vent tube is installed and clear of painted parts on the bike.
During the off season: It's a good idea to remove the battery from
the bike to prevent leakage and corrosion. Check the electrolyte and
keep the battery charged. Either use the "battery tender" type
charger (which maintains the correct "float" voltage) or, one or two
days each month, use a trickle charger. Remember to charge in a well
ventilated place. Garages work well. The cold doesn't hurt them much
if the battery has a good charge, and neither does storing it on a
cement floor. (Those are myths.)
3.4 Battery Sensor: (Not all models) [Top]
There is a battery sensor on this bike. It consists of a single wire
and electrode which replaces the third cell cover from the negative
terminal on the battery. This sensor tells the dashboard computer a
couple of things.
1) If the battery is working correctly, the electrode will sense
between 4 and 6 volts.
2) If the battery electrolyte is low in the third cell, the sensor
will no longer be submerged in electrolyte, causing no voltage to be
sensed, and triggering the "batt" warning light.
3) If the battery voltage is to low, due to a charging problem, the
voltage in the third cell will also be low, triggering the "batt"
warning light.
The sensor tip requires periodic cleaning. Over time, the tip of the
sensor will become plated with lead sulfate, causing a resistive
drop, and making the "batt" light come on. Clean the tip with
scotch-bright, emery cloth, fine sand paper, etc., and you'll be back
in business.
Additionally, Yuasa warns that different batteries use different size
and shape sensors. If you switch battery brands or models, check to
see if a new sensor is available for that battery.
4. Starter Solenoid:
The starter solenoid is an electromechanical device that allows power
to be applied to the starter motor remotely. It is simply a big
single pole relay. Inside the solenoid there is a 12 volt
electromagnetic coil, which, when energized, closes heavy duty
contacts, allowing current to flow between the two big terminals.
There are four terminals altogether, the two big terminals, and the
two coil wires which are soldered to the solenoid and plug into the
wiring harness with a two wire connector. The solenoid is located
next to the battery.
In general, when solenoids die, it is because the coil has developed
either a short or open circuit. A short will most likely blow a fuse.
If the coil is open circuit, it won't even click if you push the
button.
The internal contacts can also stop working. This is usually
indicative of a problem with the load or power supply (starter motor
or battery) caused by excessive sparking or current. One owner
reported repairing the internal contacts by opening the solenoid and
soldering in new home made contacts, with good results. The solenoid
is not designed for this, but its an option of you feel capable.
It is most common, however, for a solenoid to *seem* dead because of
wiring problems, corrosion, etc.
4.1 Checking the Solenoid:
If you have an intermittent starting problem, don't suspect the
solenoid first. The most likely causes are wiring, connectors and
switches. See the section on corrosion for details. Check the starter
switch, fuses, interlock switches and relays, and all the connectors.
If you suspect the solenoid is not working, the first thing to do is
to confirm that the rest of the bike is in proper working order.
Carefully pull aside the rubber terminal covers on solenoid. Use
caution, as the contacts are still live. With the bike ignition
turned on, be certain the bike is in neutral, short the big terminals
with an insulated screwdriver. (Keep your fingers away and don't
touch the frame of the bike with the screwdriver!) A spark should
fly, and the bike should turn over. If the engine doesn't turn over,
this means something other than the solenoid is not working (suspect
the battery, the starting motor, and wiring). Fix this problem before
reassessing the solenoid.
If the engine does turn over, then the problem exists in either the
solenoid, the wiring between the solenoid and the starter button,
relays, or the starter button itself. In order to narrow it down to
just the solenoid, apply 12 volts directly to the coil wires to see
if the bike starts. Disconnect the two wire connector from the
solenoid. Then, using some wire, apply 12 volts to the connector
directly from the battery. This should cause the solenoid to click
and start the bike. (Again, be certain you are in neutral.) If it
doesn't, double check all of the solenoid's external wiring and
connector for breakage or corrosion. If there is nothing external to
fix, then it is time to replace the solenoid.
5. The Starter:
Its a fine starter, as starter motors go. The most common problem is
the starter spinning but not engaging. This is a mechanical problem
in the starter clutch, usually having to do with the starter drivers,
and will not be dealt with here.
A few XJ owners have had to repair or replace the starter. Some
simply needed new brushes, which are available at a premium from
Yamaha. (One owner was able to modify generic brushes to do the
trick.) Others had to resurface the commutator, and cut back the mica
separators.
If you think your starter may be malfunctioning, see the manual
excerpt for information on repairing it. Note that if you replace the
brushes yourself, it is extremely important to be sure they make very
good contact with the commutator.
The biggest problem I have with the starter is that it is too good.
In an automobile, the first thing affected by a weak battery is the
starter (or starter solenoid.) The design in a car means that if you
have enough juice to engage the starter and turn the engine over, you
have enough power to get everything else going, i.e., the ignition.
This is not the case with this bike. The bike will crank fine with a
weak battery, even if there isn't enough "left over" to spark the
ignition. This can be very frustrating.
Solution: Don't have a weak battery. Don't have resistive drops in
the path to the ignition module and coils.
6. Alternator/Rectifier/Regulator:
This bike uses Hitachi's three phase regulated alternator. What this
means is, instead of rotating a permanent magnet around or inside
stator coils, generating a voltage, the regulated alternator uses
what is essentially a variable rotating electromagnet. This
"electromagnet" rotor is fed a current which is adjusted to keep the
output of the alternator between 14.2 and 14.8 volts (with no load).
The regulator/rectifier box is the gadget that does this adjusting.
The rectifier part simply converts the 3 phase AC output of the
alternator into (somewhat ripply) direct current using diodes. The
regulator part is where the magic occurs.
First, the regulator must know what voltage is coming out of the
alternator. So it looks at a brown wire that comes from the front of
the bike via the ignition switch. This wire gets its power from the
ignition switch and also feeds the fuses in the secondary circuits
(ignition, headlights, etc.) The ignition switch gets ITS power from
both the rectified output of the alternator and the battery (red
wires). This is a very long loop (see Battery Overcharging for
details.)
The regulator looks at the voltage on the brown wire, then pushes an
appropriate amount of current through the rotor windings to make the
output voltage (red wire) right. On these bikes the rotor wires are
green and brown (actually the same brown wire as above), and are
connected to the regulator/rectifier box. The green wire is the one
that does all the work. If you measure the voltage on the green wire
(between green and ground) you should see it go from about 1.8 volts
at 2000 rpm up to 9-11 volts when you rev the engine, as the
regulator does its thing.
6.1 Alternator Connections:
There are five wires connected to the alternator. Two, (brown and
green) feed the rotor from the voltage regulator. Corrosive
resistance drops in the connectors for these wires can keep the
regulator from reaching the proper voltage.
Three (white) wires comprise the alternator's output. These wires,
which carry three-phase alternating current, go to the rectifier
(part of the voltage regulator), where the power is converted to
direct current. A common problem is corrosion in the connections
under the seat and on the regulator. This causes the alternator to
work too hard and can melt connectors.
6.2 Alternator brushes:
Alternator brushes are fed by the rotor wires. The brushes, made of
pressed carbon, maintain electrical contact with the rotor while it
is spinning. Removing the (left) cover of the alternator will allow
you to examine the brushes.
The brushes only carry the current needed to "excite" the moving
magnetic field in the alternator (an amp or so.) The big output
current of the alternator comes from the stator wires, and they have
no moving parts. This is part of the reason the brushes last so long.
The brushes are pretty hefty to start. The biggest concern, then, is
not that they will wear out, but that the electrical characteristics
of the brushes will change. The brush material can absorb oil
(especially if you lay the bike on its left side!), and just "age" in
general, becoming more resistive. As long as the bike's electrical
system is capable of reaching the regulated voltage, there is no
problem.
6.3 Regulator box:
The regulator box contains both the regulator and the rectifier. It
is located on the left side of the bike, near the ignition. It has
large heat-sink fins, and the internal circuitry is "potted" in
epoxy. The most common problem is corrosion in the connector. The
next most common problem is with rectifier diodes burning out.
The unit is generally very reliable. You can verify proper operation
by measuring the regulated voltage on the red wire with the battery
fully charged and the bike running. You should also measure the
voltage on the green wire as you rev the engine. This should start at
1.8 Volts at idle and increases to about 10 or 11 Volts as rpms are
increased. (See the manual excerpt for details.)
6.4 Checking Diodes:
There are six diodes in the rectifier. Since the entire circuit is
embedded in epoxy, it is not possible to repair them. It is possible
to check them, though.
First, disconnect the regulator box from the wiring harness. Then,
using a voltmeter with diode checking, check between each of the
three white wires and the red output wire. For each white wire, you
should "see" a diode pointing towards the red wire. Next, check each
white wire against the black ground wire. This time, you will "see"
diodes pointing from ground toward each of the three wires.
If one of the diodes is fried, like an open circuit, it is possible,
if you are crafty, to add a new diode externally. If any of them are
short circuited, you'll need to replace the rectifier.
7. Ignition:
This bike uses a Transistor Controlled Ignition (TCI), not a
Capacitive Discharge Ignition (CDI). TCI's are known to be finicky
about supply voltage. (This is because the circuit requires a minimum
voltage just to get all the transistors into their "operating"
state).
The TCI gets its ignition timing information from two pick-up coils
on the left end of the crankshaft. The timing is not adjustable, and
the TCI determines advance internally, based only upon rpm. There is
no distributer, vacuum, or mechanical advance on this bike. Although
the timing is not adjustable, you can verify the advance action with
a timing light by removing the left crank shaft cover.
The TCI box, located on the left side of the bike, under the side
cover, does not have internally serviceable parts. The TCI circuits
themselves are pretty reliable. The same cannot be said for the
connectors on and inside of the box. If the red wire has the proper
voltage, and the ignition is making a good spark, the TCI can be
considered good.
There have been reports of the TCI getting fried from improper
jump-starting of the bike. Keeping the ignition turned "off" while
connecting the jumper cables will probably prevent this problem.
7.1 Coils:
There are two ignition coils for the four cylinders. What this means
is that each cylinder gets twice as many sparks as it needs, one
during the compression stroke for ignition, and one during the
exhaust stroke. The only reason for the extra spark is to simplify
the ignition system and use two coils instead of four. This is
possible because the one and four cylinders and the two and three
cylinders move in synchrony (with different valve timing). This is
important to remember if you ever connect a tach to the bike, 2000
rpm will read like 4000 rpm.
The coils are pretty reliable if the connections are good and there
are no physical problems, like cracks, in the ignition wires or in
the plastic case around the coils (which can cause high voltage
leaks).
You can check the secondary resistance of each coil by removing the
plug-caps (they screw off) and measuring the resistance between the
ends of the two plug wires. The specification is 11k Ohms.
[Note: The manuals show measuring the secondary resistance with the
plug caps on. This has been determined to be incorrect by the readers
of the XJ Mailing list. Yes, Yamaha, Haynes, and Clymer all got it
wrong.]
A low resistance measurement indicates an internal short in the coil,
and results in diminished spark. A high resistance measurement also
diminishes spark somewhat. An open circuit between the plug wires
means a wire is broken, either a plug wire or an internal coil wire.
[A coil may still operate with an open circuit secondary. The voltage
spike jumps the broken wire (another spark), in addition to sparking
the two plugs. In some cases, its possible to ride for a number of
years with an internal broken wire!]
The plug-caps have been the source of problems for some XJ owners.
They are resistor caps (designed to reduce radio interference.)
Yamaha replacements are a bit expensive, but aftermarket ones from
NGK are available and are said to work well. Typically, all four caps
are replaced with NGK 5k Ohm caps.
The coils have been called "weak" on occasion by members of the
xj-owners group. To be clear, the coils aren't really weak, they just
don't operate well if the supply voltage is low. (After market coils
may help, but only slightly: They draw more current and will create a
bigger voltage drop, see headlight section for an explanation.)
Replacing the coils will not solve the underlying problem.
Since both the coil and the TCI are responsible for making a good
spark, reducing the voltage available to them amplifies any spark
problem. Reducing the voltage to the coil reduces the spark directly,
and reducing the voltage to the TCI hurts the spark further. This is
why having a good voltage supply and ground to the ignition (meaning
good, clean, uncorroded connectors) and a strong battery is essential
to keeping the bike in good working order. (And so critical in these
bikes.)
8. Headlamps, lighting, and accessories:
8.1 Upgrading:
The most common question about headlights is, "Can I make them
brighter?" The simple answer is yes, though actually making this
happen can be quite involved.
The alternator can withstand a bit of extra load. It is rated for 19
amps, and uses about 12 or so in the stock configuration (depending
on the bike). Adding two 100 watt driving lights is out of the
question, but increasing the power of the existing lights is
possible.
The standard headlight (55/65 watt) draws from 3-6 amps depending on
things like alternator voltage and resistive losses in the power
path. A high power light (55/100 watt or 85/100 watt) will increase
this draw by 3 or 4 amps. Judging from the uses of the power in the
bike, and personal experience, the alternator can handle this. But
that's not the end of the story.
8.2 A good idea?
Why is simply changing the headlight element to a high power
headlight not necessarily a good idea?
For one, you've got to consider the path the additional power must
follow. The headlight current comes from the alternator and battery
(which are connected together with the main fuse.) This power then
goes to the keyswitch, and then back to the fuse block, where the
power is split between the three remaining fuses (one being the
headlight fuse). From the headlight fuse the power goes to a relay
(which keeps the headlight from coming on until the bike is running),
then it goes to the dimmer switch on the left handlebar. From there
the power (now two wires, one for high, and one for low beam) goes to
THE COMPUTER (for models that have them).
What happens in the computer? The current goes onto the main circuit
board where each wire (high and low beam) goes to a coil which is
wrapped around a reed switch. When current is running through one of
the coils, a magnetic field is induced which triggers the reed
switch. The reed switch is connected to the computer, and allows the
computer to know when a headlight is burnt out. If a headlight is
out, no current will be in the coils and the reed switch won't
trigger--the computer sets a warning "HEAD" and a flashing light.
[If your bike does this, you can see it work by removing the
headlight and starting the bike.]
When the headlight current comes out of the coils, it leaves the
computer and goes directly to the headlight via the headlight
connector.
8.3 Where might problems arise?
1) Additional current through the headlight relay may cause the
contacts to wear out too quickly or arcweld themselves.
2) Extra current through the headlight dimmer switch may also be
beyond the designed amperage rating, causing the switch to fail.
3) Those little coils inside the computer: They might fry. They might
also short and fry the computer. They might fry the traces on the
circuit board. (Not all models)
4) Resistive voltage drops increase: Since the wire that goes through
the keyswitch shares the current for the headlight, ign, alternator
rotor, computer, other lights, (everything!), drawing extra current
down it will drop the voltage available to everything else. This can
cause a number of complicated problems, including battery
overcharging. You would have to be VERY careful to have good, clean,
connections down this path. Even 1/2 ohm of resistance will cause a
problem.
5) Can the wiring handle it? (Yes, I believe so, although making sure
you don't have corroded wires will be more important than ever.)
Why doesn't plugging in an high power headlight element seem to add
much light?
It has to do with above issue number four, resistive voltage drops.
When you plug in a high power headlight, what you are doing is
increasing the current along the power path. Any resistance along
this path will drop the voltage available to the headlight.
Simple answer: Put in a higher power headlight, but drop the voltage
available to it, and you end up with the same light output (or only
slightly better) than you started with.
Technical answer: A 55 watt light operating at 12 v (nom.) will draw
about 4.5 amps. A 100 watt draws 8 amps. If there is 1/2 ohm
resistance in the supply, the 55 watt lamp will lose about 2 volts.
The 55 watt bulb, with 10 volts will put out only about 35 watts
worth of light. For the 100 watt bulb, the voltage drop is more like
4 volts. A 100 watt bulb operating at 8 volts will put out about 45
watts worth of light. Which is not much better than what you started
with.
[I am ignoring the nonlinear characteristics of incandescent lighting
like inrush current and variable resistance due to self- heating, but
you get the idea. Comes from P=I^2*R, where power is proportional to
the square of the current...]
8.4 Recommendations:
If you really want more light, run a separate wire from the
alternator output (at the rectifier). This will reduce resistive
losses, and give you a brighter light. Once you have full power
coming out of your 85/100 watt light, you will need to take into
consideration the other problems, melting reflectors, burning out
switches etc. And if you have the computer in your bike all the
things I mentioned earlier become important.
8.5 Suggestion:
Car people do this all the time: Install separate relays for the high
power headlight, with its own power feed directly from the alternator
(put a fuse in, please!). You'll need two relays, one for high and
one for low.
Problem (Only models with computer): If you do this, you will no
longer be drawing a substantial current through the computer's coil
sensor thingy. This will trigger your "HEAD" message and flashing
light. You will need to disable it. This can be done by opening your
computer and doing magic, which I don't suggest, unless you REALLY
know what you're doing. Or, you can simply remove the bulb under the
flashing "warning" light and ignore the dashboard.
8.6 The little Driving light (Models that have it):
If your bike has one of those little driving lights under the main
headlight, there is something you can do to easily soup it up. The
OEM lamp is 35 watts. The bulb mount is identical to those off-road
driving lights made by Hella (expensive) and Ralley-X (cheap) found
in automotive stores. You can replace the bulb with a 55 watt version
(<$10). I've been doing this for years. The extra current (20
watts) is within the wiring and switches capabilities. Don't use
the 100 watt version, though, it may melt things.
[One owner reported trying the 100 watt light. He found the
illumination pattern is drastically different from stock and
practically useless.]
This little driving light does not go through the computer, but all
the other caveats apply.
8.7 Headlight Relay:
It seems not all XJ bikes have this. For those that do, the headlight
relay keeps the headlight from turning on until the bike is running.
It is also possible that this option has been bypassed after a relay
failure by a previous owner of your bike.
The headlight relay is connected to one of the output wires on the
alternator (via its own diode), and is configured as a "latch". What
this means is that the headlight doesn't come on until the alternator
is spinning fast enough to set the relay, and then it holds itself
"on" until the ignition switch is turned off.
Often, the headlight will come on during cranking even if the engine
doesn't start. This just indicates that the alternator was moving
enough to latch the relay. This is normal. Simply turn the ignition
switch to "off" then "on" to reset the relay.
This setup prevents the headlight from drawing current while the
starter is spinning, trying to get the ignition to fire up. It helps
keep the battery voltage up during cranking, and compensates somewhat
for the "weak coil" problem I mentioned earlier.
9. Computer monitor system (Not all models):
The computer monitor system on the Secas performs a number of
functions. It is not, however, as sophisticated as automobile
computers, which control fuel mixture and shift patterns.
What it does do:
The computer monitors seven things:
1) The position of the side stand.
2) Brake fluid level in the master cylinder
3) Battery electrolyte level (See above)
4) Engine oil level
5) Headlamps
6) Taillights
7) Fuel level (gauge)
The computer is just a monitor. That is to say, it takes inputs but
actually controls nothing. It contains what is probably a
microprocessor and circuits to convert the inputs into digital
signals. The only "outside" signals that pass through the computer
are the headlight and taillight currents.
The monitor system is very reliable, and the only concern is that
some of the connectors might get corroded. The dashboard "Warning
Control" and "Check" buttons are extremely reliable as they use
sealed reed switches and magnets to connect to the computer.
10. Canceling turn signal:
The self-canceling turn signal works off of a reed switch in the
speedometer. It is generally reliable, although problems have been
frequently seen in the turn signal switch itself.
If you experience problems with getting the turn signals to engage,
disassemble and clean the switch.
When one of the turn signal bulbs is burnt out, the signal will not
flash. This is characteristic of the design, and is helpful to alert
you to a bad bulb. Reduced voltage from connector corrosion can cause
the same effect, as can a dying turn signal relay.
11. Overcharging: (You've heard so much about it!) [Top]
It seems counter-intuitive, but one of the most common electrical
problems with this bike is battery OVER-charging due to corroded
connectors. This really does happen. Here's why:
The first thing to examine is how the alternator and voltage
regulator work. As mentioned earlier, the bike uses what is called a
regulated alternator. The regulator "measures" the voltage in the
bike's wiring harness and "programs" the alternator to make enough
power to keep the voltage at the right level. It is a very simple
"feedback" loop.
This is a great setup, the regulation is simple, and because the
output of the alternator is variable, wastes less energy, and puts
less drag on the engine at high rpm's. (more HP's!) It also saves the
expense of really big transistors and heat sinks to regulate the full
19 amp output of the alternator.
The implementation, however, has a problem. Yamaha engineers chose to
measure the regulated voltage after the key switch, about five feet
of wire and seven or so connectors away from the alternator output.
(This is necessary so that the measuring circuit and rotor coil will
not draw power from the battery when the bike is off.)
But, there are those seven connectors and all that wire. This is an
invitation for an inaccurate measurement. This is due to resistance
along the path.
How much does this matter? Well, since the motorcycle (neglecting the
battery) draws between 5 and 10 amps down this wire to power things
like the headlights, ignition, etc., a total resistance in this path
of only 1/2 ohm will make the alternator output RISE between 2.5 and
5 volts to compensate. This is bad.
There are two reasons this is bad. In the 1/2 ohm example, the
alternator is making 12.5 to 50 watts of power more than the bike
needs. Where does this power go? Let's say that one of the connectors
is introducing 1/2 ohm of resistance due to corrosion. The connector
will heat up. It might even melt. Could be a serious problem. And
often is. Even if it doesn't melt, you just lost about 1/10 of a
horsepower.
The second, and more important, reason this is bad:
11.1 Batteries Boiling (or how Yamaha keeps Yuasa in business..)
The battery is connected much closer to the output of the alternator.
In fact, it is connected directly to the red wire of the output
through the main fuse. When the alternator output rises by 2.5 to 5
volts as in the above example, the battery will now be "seeing" a
full 17 to 19.5 volts (14.5 + 2.5 or 5)!! This WILL overcharge your
battery. In the least severe case, you will be constantly be adding
distilled water and replacing your battery every other year. In the
most severe case, the battery will die a quick death with distended
sides and your mechanic claiming, "But the regulator tested fine..."
11.2 Solutions:
Yamaha's design is sound as long as the resistance in the loop is low
enough. When the bike comes from the factory, there is no corrosion
in the connectors. The internal resistance of the wires is very small
(I would guess less than 0.05 ohm total), resulting in a very small
difference between the brown and red wires (about 0.25 volts). This
difference will not boil batteries.
The solution is simple: Don't let connectors get corroded. Fix or
replace connectors that are.
12. Corrosion, Connectors, and Rants:
12.1 Fixing corroded connectors:
Vehicle manufacturers have only recently seemed to get there acts
together as far as proper electrical connections are concerned. The
key is to keep air away from the metal. The best way is to
butt-splice two wires together, solder, spray with "High-tack" or
some other sealant, and cover with heat-shrink tubing. It will never
corrode.
["High-tack" is a sticky red spray that mechanics use to hold gaskets
in place while installing them. Its thick and sticky nature keeps air
away from the metal making it great for this application. It's an
insulator, and doesn't ever really dry. It can be found in any auto
parts store. (This stuff is also great to spray on battery terminals
after they are connected...)]
12.2 The next best way:
Not all connections should be made permanent. Use the best connectors
you can find. You can fill the backs of the connectors with silicone
caulk, or silicone dielectric grease to keep as much air out as
possible, or use big heat shrink tubing, or tight electrical tape to
make the connectors last longer. Do it properly now and you won't be
re-doing it in two years. Crimp AND SOLDER if possible.
12.3 CORRODED CONNECTORS DON'T ALWAYS LOOK CORRODED:
There are a couple of ways to track down corroded connectors. Of
course, you can just pull them apart and look at them, but this
doesn't always work. It doesn't take much to make 1/4 ohm of
resistance with corrosion. Often you can't see the corrosion, or the
offending oxide is lurking between the crimp of the connector and the
strands of the wire. Or even surface oxidation, which slightly
changes the color of the metal could be enough to make problems.
Remember what I said about connectors getting hot and melting? Well,
feel them while the bike is running. They shouldn't even be warm, you
may not be able to tell with your fingers, so press them against your
cheek. Seriously, this works great on connectors carrying large
currents. (like the ones I am complaining about.) Don't electrocute
yourself.
You can measure the VOLTAGE drop across the connector with a
voltmeter while the bike is operating. Don't stick the probes
directly into the connector, though, because sometimes the corrosion
is between the crimp and the wire. Find where the wire comes from and
goes to, and measure from there. Rule of thumb --a volt or two drop
(on a 12V system) is bad.
[Note: Measuring the RESISTANCE across connectors is NOT a good way
to identify corrosion problems. In many cases, the resistance is too
low for a meter to accurately measure (less than 1 ohm), but can
still cause a problem. Also, a multimeter uses a very small current
to measure resistance. Many of the connectors carry large currents.
The actual resistance of the connector at its normal operating
current can be different, due to self heating and other effects.]
You can even accomplish a lot with a little sandpaper or emery board.
Beware, however, of removing plating from connectors, often the base
metal will corrode quicker than the plating did...
[An industrial contact cleaner called Cramolin (now called DeOxit)
has been suggested for yearly connector maintenance. Although it is
very good, it is expensive and difficult to obtain for lay-people.
Avionics technicians often use it, so you might be able to get it
from your local airplane mechanic. Diluted versions are sometimes
available in electronics supply stores, some of which aren't worth
spit. WD-40 is a fair alternative, as are some products by CRC.]
12.4 Where do I start?
For the overcharging problem, the critical connections are:
- the brown wire at the voltage regulator
- the brown and red wires on the ignition switch connector behind
the headlight.
- the red and black wires on the voltage regulator
You really should check every connector on the bike, because there
are other things that can go wrong. For example, weak spark from
corrosion in the ignition supply line (engine stop switch, relays,
etc.,) can cause the ignition to cut out intermittently. It is also
important to check all wires that carry large currents, like the wire
to and from the battery, battery connections, solenoid, starter, etc.
12.5 Editorial comment on connectors:
Electrical connections are often poorly done. Especially by
mechanics. You can save yourself a lot of heartache and money by
suspecting connections FIRST. It is very common for a motorcycle shop
to unwittingly (or otherwise) install a brand new part, complete with
new, uncorroded connectors, so solve what is really just a connector
problem.
In my earlier example, the overcharging problem, replacing the
ignition switch and the voltage regulator would likely have
introduced enough new, uncorroded connectors to solve, or reduce,
battery overcharging. This will cost you quite a bit more than simply
fixing the connectors yourself.
Engineers design their "little boxes" very well in general. There are
all sort of neat things that you don't hear about like current
limiters and thermal shutdown circuits designed into voltage
regulators and electronic ignitions that make them very reliable.
Please don't insult these guys by assuming they are broken just
because a Yamaha accountant didn't think good connectors were cost
effective.
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© 1998, Aaron Berg [Seca750@geocities.com]
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