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Kawasaki Ninja 650R (ER-6F) & ER-6N Resource
Charging System Troubleshooting Guide
By: Kiwi
A number of owners have reported that their Regulator/Rectifier (R/R) have failed, often this was preceded by a headlight failure and a flat battery leading to starting issues. Troubleshooting found that not only had the R/R failed but in some cases the R/R electrical connector had melted with some pins showing signs of corrosion. The headlight issue was later traced to the headlight relay.
Troubleshooting Index
1. SystemOverview
2. ComponentsandLocations
3. Circuit Diagram
4. Common Problems and Remedies 5. BatteryChecks
6. Rotor/Stator Checks
7. Regulator/Rectifier Checks
8. Regulator/Rectifier Connector
Tools Required
• Digital Multimeter and test leads with a male & female spade fittings
• Tools required for access (spanners, allen keys, sockets and screwdrivers)
Charging System Overview
In simplified terms the Ninja 650R (ER-6F) and ER-6N uses a stationary Stator Coil mounted to the left hand crankcase cover, it sits inside the flywheel Rotor. The Rotor has magnets so that when the engine is running these rotate around the Stator producing alternating current (AC). The Stator is wired in such a way that there are actually 3 circuits which produce a 3 phase AC output voltage.
This Alternator (Rotor/Stator) setup is connected to a Regulator/Rectifier (R/R) by 3 wires. The R/R rectifies the AC current by using 6 diodes (2 per phase) and converting it to a useable direct current (DC). The more complex part of the R/R is the regulator section, it regulates the higher DC current down to provide a steady 12-14 volts DC. The process in simplest terms monitors the output voltage and "shunts" (partially diverts) the excess portion to ground through a “load”.
The R/R has a lot of current constantly flowing through it and the excess voltage is being diverted to ground through the “load” so the R/R gets very hot in the process. The construction of the R/R is all about dissipating this heat through the heat fins on its exterior.

Kawasaki Ninja 650R (ER-6F) & ER-6N Resource
Components and Locations
Stator – removed
Stator – mounted in left hand crankcase cover
Rotor – left hand crankcase cover removed

Kawasaki Ninja 650R (ER-6F) & ER-6N Resource
Regulator/Rectifier – below seat left hand side
Relay Box – under fuel tank
Relay Box
Kawasaki Ninja 650R (ER-6F) & ER-6N Resource
Battery – underseat (black terminal –ve) (red terminal +ve)
Circuit Diagram
1. IgnitionSwitch
2. Alternator
3. Rectifier/Regulator 4. Water-proof Joint 5. Main Fuse 30 A
6. Battery12V10Ah 7. Load
Wiring Colour Code
BK
Black
BR
Brown
GY
Gray
BL
Blue
G
Green
LB
Light Blue
LG
Light Green
O
Orange
P
Pink
PU
Purple
R
Red
W
White
Y
Yellow

Kawasaki Ninja 650R (ER-6F) & ER-6N Resource
Common Problems and Remedies
Failure of the Regulator/Rectifier (R/R) is often first evidenced by a flat battery and starting issues. Troubleshooting should always start with the battery.
Make sure you have a good battery. A bad, old or dead battery will load down the charging circuit until it overheats and dies. You know when you put a dead battery on charge and it pegs the battery charger ammeter? Well that is what a bad battery is doing to charging components on your bike.
Having said that. Numerous posts on internet forums with this fault have indicated that most often a failed R/R is the culprit. This is often in association with corroded or damaged pins on R/R electrical connector or loom plug pins. It may be that these are just the weakest link in the chain.
Damaged Regulator/Rectifier Loom Plug

Kawasaki Ninja 650R (ER-6F) & ER-6N Resource
Damaged Regulator/Rectifier connector pins
Those who have experienced headlight issues also find that the headlight relay is at fault. The headlight relay is part of the Relay Box and also contains 3 diodes. Posts to date do not indicate whether it is the diodes or the actual headlight relay at fault. Unfortunately the individual relays and diodes cannot be replaced and the relay box is sold as a complete unit.
The Service Manual has a complete series of tests for both the headlight relay and diodes, as the Relay Box is not a cheap item it would be advisable to confirm serviceability before making an expensive purchase.
The Battery
The following is taken from the Ninja 650R (ER-6F) & ER-6N Battery FAQ.
Is it the battery, or the charging system, or something in-between? The best way to know for sure is to use a Multimeter selected to DC Volts (20 volt range) attached directly to the battery positive and negative terminals, and observe the following:
1. With the engine and all electrical accessories switched off, the battery should read a minimum of 12.7 volts DC. If not, the battery is either not fully charged, or it is bad (it is incapable of holding a full charge).
Charge the battery fully with a battery charger and check again. Remember however that you must wait at least one hour after charging the battery to conduct this test. Then if the reading is less than 12.7 volts DC, the battery is bad and should be replaced.
Kawasaki Ninja 650R (ER-6F) & ER-6N Resource
State of Charge
Digital Voltmeter
100%
12.7 volts DC
75%
12.4 volts DC
50%
12.1 volts DC
25%
11.9 volts DC
0%
11.8 volts DC
2. If the first test above passes, leave the Multimeter hooked up to the battery terminals, and press the starter button. While the starter is engaged (but before the bike starts) the battery voltage should be 9.5 volts DC or greater. If not, then this signals either a bad battery, very dirty or weak electrical connections, or it could be a problematic starter motor (not likely it's probably the battery).
3. The charging system output voltage should be checked, again with the multimeter at the battery terminals and this time with the engine is running.
Start the engine and operate at various RPM with the headlight on and off (to turn off the headlight, disconnect the headlight connector).
The readings may show nearly battery voltage when the engine speed is low, and, as the engine speed rises, the readings should also rise. But they must be kept under the specified voltage.
According to the Kawasaki Service Manual the measured voltage should be 14.2 - 15.2 volts DC at about 2000-3000 rpm. In reality it is more likely to be in the range of 13.5 – 15.0 volts DC.
NOTE: If the alternator is outputting more than 15.2 volts DC to the battery, the Regulator/Rectifier (R/R) unit is bad and should be replaced. Over-charging a battery will quickly ruin it and may cause severe damage or failure of other electrical components such as the ECU.
If the charging voltages are too low and do not rise as engine speed increases, suspect the alternator or R/R.
If the charging voltages are too high, suspect the R/R unit firstly, then perhaps dirty or corroded electrical terminals. The procedure for checking all of these is too detailed to describe here so consult the Service Manual for additional details.
4. Although is not related to charging system, another issue such as wiring or an accessory may be causing battery discharge. To check this carry out a current leakage check as follows:
Ensure the battery is fully charged and check that the battery voltage measures above 12.7 volts DC (test 1 above). Disconnect the negative (black –ve) lead from the battery terminal (stud). Measure the Leakage Current of the bike by setting the multimeter to DC Amps, connect one multimeter probe to the battery negative terminal and connect the other multimeter probe to the negative lead. The current should be no higher than about 5.0 mA (milliamps) with the ignition switched OFF. In reality you should expect to see around 1.0 to 2.0 mA.
If Current Leakage exceeds 5.0 mA, there is a fault with wiring harness an accessory such as an alarm or the R/R draining the battery. Try pulling fuses or disconnect the R/R to locate the problem.
Kawasaki Ninja 650R (ER-6F) & ER-6N Resource
The Rotor/Stator
To check the integrity of the stator there are a number of tests that can be carried out. The integrity of the Rotor is more difficult to test and in reality can only be confirmed serviceable by swapping with a known good part. As the only thing likely to go wrong with a Rotor is a loss of magnetism (and that is very unlikely) then this should only be considered when there is no alternator output voltage and all the other tests have checked out OK.
1. To carry out a resistance check of the Stator windings use a Multimeter selected to Ohms (Ω range). Connect the multimeter leads and measure the resistance between each “pair” of windings. Black wire to black wire pins, 1-2, 2- 3 & 1-3.
There are two points where this can be done easily, the connector at the Regulator/Rectifier R/R) or you can follow the 3 wires out of the left hand crankcase cover up to an Alternator Lead connector.
Alternator Lead connector
The resistance between each pair of wires should be in the 0.18 - 0.27 ohms range.
A very low winding resistance could be a shorted winding although that is not that common, what normally happens is they burn through and go open circuit with infinite resistance (multimeter displays dashed lines or the abbreviation "OL" which stands for "open loop"). In either case the Stator will require replacement.
A “cooked” Stator is usually obviously when removed with a burnt look to the windings and insulation.