Yamaha MT-03 - Service manual > Electrical components

Electrical system / Electrical components

Electrical components

Starter relay
Main fuse
Battery
Fuel pump
Throttle position sensor
Coolant temperature sensor
Fuel injector
ECU (electronic control unit)
Lean angle cut-off switch
Turn signal/hazard relay
Headlight relay
Radiator fan motor relay
Relay unit
Rectifier/regulator
Sidestand switch
Crankshaft position sensor
Stator coil
Horn

Electrical components

Front brake light switch
Right handlebar switch
Clutch switch
Left handlebar switch
Main switch
Immobilizer unit
Ignition coil
Plug cap
Spark plug
Intake air pressure sensor
Fuse box
Rear brake light switch
Intake air temperature sensor
Neutral switch
Starter motor
Speed sensor
Radiator fan motor
Air induction system solenoid

Checking the switches

Checking the switches

Main switch
Clutch switch
Horn switch
Pass switch
Dimmer switch
Turn signal switch
Hazard switch
Sidestand switch
Front brake light switch
Engine stop switch
Start switch
Neutral switch
Rear brake light switch
Fuses

Check each switch for continuity with the pocket tester. If the continuity reading is incorrect, check the wiring connections and if necessary, replace the switch.

CAUTION:

Never insert the tester probes into the coupler terminal slots "a". Always insert the probes from the opposite end of the coupler, taking care not to loosen or damage the leads.

Pocket tester 90890-03112

NOTE:

Before checking for continuity, set the pocket tester to "0" and to the "Ω x 1" range.
When checking for continuity, switch back and forth between the switch positions a few times.

Checking the switches

The switches and their terminal connections are illustrated as in the following example of the main switch.

The switch positions "a" are shown in the far left column and the switch lead colors "b" are shown in the top row.

The continuity (i. e., a closed circuit) between switch terminals at a given switch position is indication by " " There is continuity between red, brown/blue, and brown/red when the switch is set to "ON" and between red and brown/red when the switch is set to " ".

Checking the switches

Checking the bulbs and bulb sockets

NOTE:

Do not check any of the lights that use LEDs.

Check each bulb and bulb socket for damage or wear, proper connections, and also for continuity between the terminals.

Damage/wear → Repair or replace the bulb, bulb socket or both.

Improperly connected → Properly connect.

No continuity → Repair or replace the bulb, bulb socket or both.

Types of bulbs

The bulbs used on this vehicle are shown in the following illustration.

Bulbs "a" and "b" are used for the headlights and usually use a bulb holder that must be detached before removing the bulb. The majority of these types of bulbs can be removed from their respective socket by turning them counterclockwise.
Bulbs "c" are used for turn signal and tail/brake lights and can be removed from the socket by pushing and turning the bulb counterclockwise.
Bulbs "d" and "e" are used for meter and indicator lights and can be removed from their respective socket by carefully pulling them out.

Types of bulbs

Checking the condition of the bulbs

The following procedure applies to all of the bulbs.

1. Remove:

Bulb

WARNING

Since headlight bulbs get extremely hot, keep flammable products and your hands away from them until they have cooled down.

CAUTION:

Be sure to hold the socket firmly when removing the bulb. Never pull the lead, otherwise it may be pulled out of the terminal in the coupler.
Avoid touching the glass part of a headlight bulb to keep it free from oil, otherwise the transparency of the glass, the life of the bulb, and the luminous flux will be adversely affected. If a headlight bulb gets soiled, thoroughly clean it with a cloth moistened with alcohol or lacquer thinner.

2. Check:

Bulb (for continuity) (with the pocket tester) No continuity → Replace.

Pocket tester 90890-03112

NOTE:

Before checking for continuity, set the pocket tester to "0" and to the "Ω x 1" range.

Check each bulb and bulb socket for damage

a. Connect the positive tester probe to terminal "1" and the negative tester probe to terminal "2", and check the continuity.

b. Connect the positive tester probe to terminal "1" and the negative tester probe to terminal "3", and check the continuity.

c. If either of the readings indicate no continuity, replace the bulb.

Checking the condition of the bulbs

Checking the condition of the bulb sockets

The following procedure applies to all of the bulb sockets.

1. Check:

Bulb socket (for continuity) (with the pocket tester) No continuity → Replace.

Pocket tester 90890-03112

NOTE:

Check each bulb socket for continuity in the same manner as described in the bulb section; however, note the following.

a. Install a good bulb into the bulb socket.

b. Connect the pocket tester probes to the respective leads of the bulb socket.

c. Check the bulb socket for continuity. If any of the readings indicate no continuity, replace the bulb socket.

Checking the leds

The following procedures applies to all of the LEDs.

1. Check:

LED (for proper operation) Improper operation → Replace.

a. Disconnect the meter assembly coupler (meter assembly end).

b. Connect two jumper leads "1" from the battery terminals to the respective coupler terminal as shown.

Checking the leds

Immobilizer system indicator LED

Connect the pocket tester (kΩ x 1) to the meter coupler.

WARNING

A wire that is used as a jumper lead must have at least the same capacity of the battery lead, otherwise the jumper lead may burn.
This check is likely to produce sparks, therefore, make sure no flammable gas or fluid is in the vicinity.

CAUTION:

Do not connect the jumper lead (battery voltage) to the terminals (green/blue and black/white) for the immobilizer system indicator light (LED). The LED could be damaged.

c. When the jumper leads are connected to the terminals, the respective LED should illuminate.

Does not light → Replace the meter assembly.

Checking the fuses

The following procedure applies to all of the fuses.

CAUTION:

To avoid a short circuit, always turn the main switch to "OFF" when checking or replacing a fuse.

The main fuse is located under the fuel tank.

The fuse box which contains the fuses for the individual circuits is located under the rider seat.

1. Remove:

Seats
Fuel tank

2. Check:

Fuse

a. Connect the pocket tester to the fuse and check the continuity.

NOTE:

Set the pocket tester selector to "Ω x 1".

Pocket tester 90890-03112

b. If the pocket tester indicates "∞", replace the fuse.

3. Replace:

Blown fuse

a. Turn the main switch to "OFF".

b. Install a new fuse of the correct amperage rating.

c. Set on the switches to verify if the electrical circuit is operational.

d. If the fuse immediately blows again, check the electrical circuit.

WARNING

Never use a fuse with an amperage rating other than that specified. Improvising or using a fuse with the wrong amperage rating may cause extensive damage to the electrical system, cause the lighting and ignition systems to malfunction and could possibly cause a fire.

4. Install:

Fuel tank
Seats

Checking and charging the battery

WARNING

Batteries generate explosive hydrogen gas and contain electrolyte which is made of poisonousand highly caustic sulfuric acid.

Therefore, always follow these preventive measures:

Wear protective eye gear when handling or working near batteries.
Charge batteries in a well-ventilated area.
Keep batteries away from fire, sparks or open flames (e.g., welding equipment, lighted cigarettes).
DO NOT SMOKE when charging or handling batteries.
KEEP BATTERIES AND ELECTROLYTE OUT OF REACH OF CHILDREN.
Avoid bodily contact with electrolyte as it can cause severe burns or permanent eye injury.

FIRST AID IN CASE OF BODILY CONTACT: EXTERNAL

Skin - Wash with water.
Eyes - Flush with water for 15 minutes and get immediate medical attention.

INTERNAL

Drink large quantities of water or milk followed with milk of magnesia, beaten egg or vegetable oil. Get immediate medical attention.

CAUTION:

This is a sealed battery. Never remove the sealing caps because the balance between cells will not be maintained and battery performance will deteriorate.
Charging time, charging amperage and charging voltage for an MF battery are different from those of conventional batteries.

The MF battery should be charged as explained in the charging method illustrations.

If the battery is overcharged, the electrolyte level will drop considerably.

Therefore, take special care when charging the battery

NOTE:

Since MF batteries are sealed, it is not possible to check the charge state of the battery by measuring the specific gravity of the electrolyte.

Therefore, the charge of the battery has to be checked by measuring the voltage at the battery terminals.

1. Remove:

Seats
Fuel tank
Battery cover

CAUTION:

First, disconnect the negative battery lead "1", and then positive battery lead "2".

Checking and charging the battery

3. Remove:

Battery band
Battery

4. Check:

Battery charge

a. Connect a pocket tester to the battery terminals.

Positive tester probe → positive battery terminal
Negative tester probe → negative battery terminal

NOTE:

The charge state of an MF battery can be checked by measuring its open-circuit voltage (i.e., the voltage when the positive battery terminal is disconnected).
No charging is necessary when the open-circuit voltage equals or exceeds 12.8 V.

b. Check the charge of the battery, as shown in the charts and the following example.

Example

Open-circuit voltage = 12.0 V

Charging time = 6.5 hours

Charge of the battery = 20-30%

5. Charge:

Battery (refer to the appropriate charging method)

WARNING

Do not quick charge a battery

CAUTION:

Never remove the MF battery sealing caps.
Do not use a high-rate battery charger since it forces a high-amperage current into the battery quickly and can cause bat-tery overheating and battery plate damage.
If it is impossible to regulate the charging current on the battery charger, be careful not to overcharge the battery.
When charging a battery, be sure to remove it from the vehicle. (If charging has to be done with the battery mounted on the vehicle, disconnect the negative battery lead from the battery terminal.)
To reduce the chance of sparks, do not plug in the battery charger until the battery charger leads are connected to the battery.
Before removing the battery charger lead clips from the battery terminals, be sure to turn off the battery charger.
Make sure the battery charger lead clips are in full contact with the battery terminal and that they are not shorted. A corroded battery charger lead clip may generate heat in the contact area and a weak clip spring may cause sparks.
If the battery becomes hot to the touch at any time during the charging process, disconnect the battery charger and let the bat tery cool before reconnecting it. Hot batteries can explode!
As shown in the following illustration, the open-circuit voltage of an MF battery stabilizes about 30 minutes after charging has been completed. Therefore, wait 30 minutes after charging is completed before measuring the open-circuit voltage.

Charging method using a variable-current (voltage) charger

a. Measure the open-circuit voltage prior to charging.

NOTE:

Voltage should be measured 30 minutes after the engine is stopped.

b. Connect a charger and ammeter to the battery and start charging.

NOTE:

Set the charging voltage at 16-17 V.If the setting is lower, charging will be insufficient. If too high, the battery will be over-charged.

c. Make sure that the current is higher than the standard charging current written on the battery.

NOTE:

If the current is lower than the standard charging current written on the battery, set the charging voltage adjust dial at 20-24 V and monitor the amperage for 3-5 minutes to check the battery.

Standard charging current is reached Battery is good.
Standard charging current is not reached Replace the battery.

d. Adjust the voltage so that the current is at the standard charging level.

e. Set the time according to the charging time suitable for the open-circuit voltage.

Refer to "Battery condition checking steps".

f. If charging requires more than 5 hours, it is advisable to check the charging current after a lapse of 5 hours. If there is any change in the amperage, readjust the voltage to obtain the standard charging current.

g. Measure the battery open-circuit voltage after leaving the battery unused for more than 30 minutes.

12.8 V or more --- Charging is complete.

12.7 V or less --- Recharging is required.

Under 12.0 V --- Replace the battery.

Charging method using a constant voltage charger

a. Measure the open-circuit voltage prior to charging.

NOTE:

Voltage should be measured 30 minutes after the engine is stopped.

b. Connect a charger and ammeter to the battery and start charging.

c. Make sure that the current is higher than the standard charging current written on the battery.

NOTE:

If the current is lower than the standard charging current written on the battery, this type of battery charger cannot charge the MF battery.

A variable voltage charger is recommended.

d. Charge the battery until the battery's charging voltage is 15 V.

NOTE:

Set the charging time at 20 hours (maximum).

e. Measure the battery open-circuit voltage after leaving the battery unused for more than 30 minutes.

12.8 V or more --- Charging is complete.

12.7 V or less --- Recharging is required.

Under 12.0 V --- Replace the battery.

6. Install:

Battery
Battery band

7. Connect:

Battery leads (to the battery terminals)

CAUTION:

First, connect the positive battery lead "1", and then the negative battery lead "2".

Charging method using a constant voltage charger

8. Check:

Battery terminals
Dirt → Clean with a wire brush. Loose connection → Connect properly.

9. Lubricate:

Battery terminals

Recommended lubricant Dielectric grease

10. Install:

Battery cover
Fuel tank
Seats

Checking the relays

Check each switch for continuity with the pocket tester. If the continuity reading is incorrect, replace the relay.

Pocket tester 90890-03112

1. Disconnect the relay from the wire harness.

2. Connect the pocket tester (Ω x 1) and battery (12 V) to the relay terminal as shown.

Check the relay operation.

Out of specification → Replace.

Starter relay

Starter relay

1. Positive battery terminal

2. Negative battery terminal

3. Positive tester probe

4. Negative tester probe