How does this work?
Remember Choose Your Own Adventure books? Same idea. You can’t effectively read this page from the top down. You have to skip around using the links at the bottom of each test/question.
If you prefer something you can print out and take to the garage with you, download the original charts; they’re really useful. If you feel comfortable with choosing your adventure as you go, skip to start.
This page is based on charts published by Eletrex USA
Very Important:
This fault-finding chart assumes that the user has knowledge of the basics of electricity (Voltage, current, resistance, etc.), and about electrical systems on motorcycles in general. If you do not have this knowledge/experience, find someone that has and let her/him check the charging system on the bike. The use of this fault-finding chart is entirely at the risk of the user. The author cannot be held responsible for any damage that could arise from the use of this fault-finding chart.
Fully charge the battery. If the battery is not fully charged you may get wrong results using this fault-finding chart. You could just replace it with a battery off another motorcycle that has a good functioning charging system.
Use an accurate digital multimeter! RR means Regulator/Rectifier. This whole fault-fining chart only works if you have a bike with a combined regulator and rectifier (= regulator/rectifier) in a single case.
Take Notice of the Following:
Suzuki used on the older GS models three different colors for the three output wires of the stator. They were the only manufacturer doing this. The only reason for this can be to cause confusion, because the output of all three wires is the same. The colors on the wires from the stator are Yellow, White/Blue, and White/Green. On the Suzuki RR for these models we’re talking: Yellow, White/Blue, and White/Red. Just think them all being yellow, and then go on with the tests below.
Let’s Get Started
Switch the multimeter to DC Volts (DCV or Vdc). Switch the range to 20 or 50V. Connect the multimeter leads to the battery terminals. Start and rev the engine up to 2500 rpm. Check the battery vo
ltage.
[ Higher than 13.5V | Lower than 13.5V ]
Rev the engine up to 5000 rpm. Check the reading on the meter.
[ Higher than 14.8V | Lower than 14.8V ]
Charging system perfectly OK. You could still disconnect most of the connections on the bike and spray them with contact cleaner or WD40. This could prevent problems in the future
Count the Wire Colors
Count the number of different wire colors emerging from the RR. If there’s a yellow wire on a Yamaha RR, don’t count it. (It is a special output wire for switching the lights on and off.)
[ Four or Less | More than Four or No RR on the Bike ]
Permanent Magnet System
You’ve got a permanent magnet alternator system. Let the engine idle, and connect the black multimeter lead up to the battery(+). Connect the red multimeter lead up to the red (or white/red = Kawasaki) output wire of the RR. Leave the RR connected up to the bike. Check the reading on the meter. Leave the engine idling!
[ Less than 0.2V | More than 0.2V ]
Bad connection in the positive lead from RR to battery(+). Check the whole lead (suspect the connectors as well as the fusebox and fuses). Good connections are extremely important in this high current lead. Solve the problem and return to [start].
Connect the red multimeter lead up to the battery(-). Connect the black multimeter lead up to the negative output of the RR (Honda: Green, Suzuki: Black/White, Yamaha: Black, Kawasaki: Black, Other: Normally Black). If you can’t find a negative output wire, then the casing of the RR is normally the negative lead to the frame. Check the reading on the meter. Leave the engine idling!
[ Less than 0.2V | More than 0.2V ]
Bad connection in the negative lead from RR to battery(-). Check the whole lead to the battery(-). If the RR doesn’t have an output lead but uses the case as connection to the frame, clean the area where it is bolted and use new screws. Also check the connection between battery(-) and frame. Also suspect the plate on which the RR is mounted (sometimes it is rubbermounted and uses an extra cable frome this plate to the battery(-) or frame). Disconnect all suspect terminal and clean. Best solution: connect the RR straight up to the battery(-) with an extra lead. Solve the problem and return to [start].
If you have an RR with four different wire colors emerging from it find the switched +12V supply input. (Normally Honda: Black, Suzuki: Orange, Yamaha: Brown, Kawasaki: Brown, otherwise check the wiring diagram for the extra wire coming from the ignition switch). Connect the red multimeter lead to the battery(+) and the black multimeter lead to the switched +12V input wire (the one you just found). Leave the RR fully connected up to the bike and let the engine idle. Switch on the lights. Check the reading on the meter
[ Less than 0.2V | More than 0.2V | Less than four different wire colors ]
Bad connection from the battery(+) through the ignition switch to the switched +12V supply input on the RR. Check the whole electrical circuit. This is one of the most difficult faults to find. Suspect the ignition switch itself, the fusebox and its connections. The RR thinks the battery voltage is too low while the actual voltage is correct or too high. Disconnect all terminals and clean them with contact cleaner. If you have solved the problem, return to [start].
Stop the engine. Disconnect the wires emerging from the stator. These are usually three yellow (or white = Yamaha) wires. Switch the multimeter to Ohms, the lowest range on the meter. Measure the resestance between all three wires coming from the stator, so you need to take three readings.
[ At least one reading is greater than 2Ω or less than 0.5Ω | 5Ω > all readings > 0.5Ω ]
Bad Stator
Stator is at fault. Replate the stator and return to [start].
Connect one of the multimeter leads up to one of the three yellow (or white = Yamaha) wire. Connect the other multimeter load up to the engine casing. Check the reading on the meter. Make sure the connection to the casing is good!
[ No Reading | Anything between 0-100Ω ]
Switch the multimeter to AC-Voltage (Range at least to 100 Vac). Make sure you DON’T switch it to DC-Voltage (DCV or Vdc). Connect the multimeter leads between two of the three yellow (or white = Yamaha) wires emerging from the stator. Start the engine and rev it up to approximately 5000rpm. Check the reading on the meter. Switch one of the multimeter leads to another yellow (or white) wire and check the reading again. Switch the other meltimeter lead to another yellow (or white) wire, and check the reading again.
[ Three Equal Readings. All Higher than 50V | Not All Equal or One is Below 50V (AC). ]
Regulator/Rectifier Positive Test
Disconnect the RR from the bike. Switch the multimeter to the DIODE-TEST function. (The reading on the display will be in Volts now, not in Ohms!) Connect the Red multimeter lead to the Red (or White/Red = Kawasaki) output wire of the RR. Connect the Black multimeter lead to one yellow (or white = Yamaha) wire. Check the reading. Repeat this procedure for the two other yellow wires.
[ 1V or Lower on At Least One Test | 1.5V or Higher on All Tests ]
Bad Regulator/Rectifier
RR is at fault. Replace it with a new one and return to [start].
Reverse Regulator/Rectifier Positive Test
Connect the black multimeter lead to the red (or white/red = Kawasaki) output wire of the RR. Connect the red multimeter lead to one yellow (or white = Yamaha) wire. Check the reading. Repeat this procedure for the other two yellow wires.
[ Lower Than 0.2V or Higher than 1.0V on At Least One Test | ~0.50V on All Tests ]
Regulator/Rectifier Negative Test
Connect the black multimeter lead to the negative output wire of the RR (Kawasaki: Black, Yamaha: Black, Honda: Green, Suzuki: Black/White). If there is no output wire, connect the black multimeter lead to the RR case. Connect the red multimeter lead to one yellow (or white = Yamaha) wire. Check the reading. Repeat this procedure for the two other yellow wires.
[ Lower Than 1.0V on At Least One Test | 1.5V or Higher on All Tests ]
Reverse Regulator/Rectifier Negative Test
Connect the red multimeter lead to the negative output wire of the RR (Kawasaki: Black, Yamaha: Black, Honda: Green, Suzuki: Black/White). If there is no output wire, connect the black multimeter lead to the RR case. Connect the black multimeter lead to one yellow (or white = Yamaha) wire. Check the readiing. Repeat this procedure for the two other yellow wires.
[ Lower Than 0.2V or Higher Than 1.0V on At Least One Test | ~0.5V on All Tests ]
Bad Battery
As this was the last test, the only thing that can be at fault is the battery itself. Replace it with another fully charged one and return to [start].
Do You Have a Regulator/Rectifier?
Is there an RR on the bike? (Somewhere on the frame under the bodywork)
Integrated Generator
You have an integrated generator (car-type, with built in regulator and rectifier). Most of the problems with this kind of generator are bad connections, from generator to battery (battery doesn’t change), or a burned out regulator (battery-voltage too high). Sometimes, the generator itself is at foult. You could check the resistance of the fieldwinding (around 5 Ohms) and the state the brushes are in. Otherwise, leave it to an expert. After solving the problem, return to [start].
High RPM DC Test
Switch the multimeter to DC-Voltage (DCV or Vdc) Range 20 to 50V. Connect the multimeter leads to the battery terminals. Start the engine and rev it up to approximately 5000 rpm. Check the voltage reading.
[ Higher Than 14.8V | Lower Than 14.8V ]
Stop the engine. Disconnect the block connector to the generator closest to the engine. This connector must have at least three yellow (or white = Yamaha) wire in it and one or two extra ones. Switch the multimeter to the lowest Ohms-range. Measure the resistance between the two other wires, or between the single extra one (apart from the yellow ones) and the engine casing
[ Between 4 and 6 Ohms | Lower Than 3Ω or Higher Than 10Ω ]
Fieldwinding & Brushes
The fieldwinding in the generator or the brushes to the rowor are at fault. If there are any brushes inside the generator, disconnect them and measure the resistance between the two copper sliprings on the rotor. These are the rings on which the brushes run.
(If there are no brushes inside the generator, replace the fieldwinding or if that’s not possible separately, replace the whole stator and return to [start].
[ Between 4 and 6 Ohms | Lower Than 3Ω or Higher Than 6Ω ]
Bad Brushes
Wiring to the brushes or the brushes themselves at fault. Replace the brushes, check the wiring to the brushes and return to [start].
Bad Rotor
Rotor at fault. Replace it with a new one and return to [start].
AC High RPM Test
Connect one spare wire to the battery(+) terminal and connect it up to one of the extra wires that are in the block connector, apart from the yellow (or white = Yamaha) wires. Connect a second spare wire between the battery(-) and the other extra wire in the connector block. If you have only one extra wire, only connect the battery(+) wire to this one. Make sure the battery(-) is still connected to the frame. Switch the multimeter to AC Volts, range at least 100V (ACV or Vac). Start the engine and rev it up to approximately 5000 rpm. Connect the multimeter leads up between two of the yellow (or white = Yamaha) wires. Check reading on multimeter. Switch one of the multimeter leads to another yellow wire and check the reading again. Then switch the other multimeter lead and check the reading again.
[ All Readings Equal and Above 50V | Not All Equal or At Least One Below 50V ]
Stop the engine. Switch the multimeter to DC Voltage (DCV or Vdc). With the block connector disconnected as above, connect the multimeter leads up to the two extra wires in this connector (apart from the three yellow wires), this in the connector block emerging from the wiring loom, not the other side going to the generator. If there’s only one extra wire, connect it to one multimeter lead and connect the other multimeter lead to the engine casing. When you switch on the ignition, check the reading.
[ No Reading or Reading Less Than 10V | Higher Than 10V ]