Star EV BN72-14-AC-D Instruction Manual

Owner’s Manual and Service Guide
Enclosed Bus:
BN72-14-AC-D and BN72-11-AC-D (Wheelchair Accessible)

2
Thanks for buying the Star EV Enclosed Bus. This manual contains
information you will need for proper operation, maintenance, and
care of your Enclosed Bus. A thorough understanding of these simple
instructions will help you to obtain maximum enjoyment from your
new Star EV.
If you have any questions about the operation or maintenance of
your Enclosed Bus, please consult your Star EV dealer.
Read and understand this manual completely before operating your
Star EV.
This manual should be considered a permanent part of your Enclosed
Bus and should remain with the vehicle when lending or resold.

3
Vehicle Specifications
Operation
Important labels
Functions
Operational Process
Safety
Maintenance
Battery maintenance
Traction/motor maintenance
Speed controller maintenance
Brake system maintenance
Lubrication
General maintenance notes
Periodic maintenance
Storage
Troubleshooting
Electrical Diagrams
Table of Contents
4
4
5
6
7
8
12
13
13
14
14
14
17
17
21

4
1: Vehicle Specifications
1: Operation
Important Labels
Please read the following labels carefully before operating the vehicle, and prompt-
ly replace any labels which become unreadable or removed.
• Security Warning label under the dashboard
• Warning label under the dashboard
• Warning label beside the parking brake handle
Enclosed Bus BN72-14-AC-D-M and BN72-11-AC-D-Wheelchair-M (Wheelchair Accessible
model)
Passengers 14 / Wheelchair: 11+ wheel-
chair Body Material Fiberglass with steel frame and aluminum doors
Battery System Twelve 6 V (72 V) batteries,
Trojan T-105 Front Suspension Independent suspension, coil over shocks
Motor Power 9.5 hp AC motor Rear Suspension
Integral rear axle, coil spring
non-independent suspension,
hydraulic shock absorber
Controller Power 550 A Curtis AC controller Steering System Rack and pinion power
steering
Top Speed 19 mph Brake System
Front and rear drum, hydraulic
brake, mechanical parking
brake
Load Capacity 2200 lbs / Wheelchair: 1900 lbs Tire Size 155 R 12 DOT tire
Dimensions
203” x 61” x 82” (L x W x H)
Wheelchair: 207” x 61” x 82” (L
x W x H)
Tire Pressure 65 psi
Weight w/ Batteries 3100 lbs Wheel Type 12” aluminum
Ground Clearance 5.5” Roof Fiberglass
Turning Radius 20  Windshield AS1, DOT automotive wind-
shield
Wheel Base 108” / Wheelchair: 104” Drive Train Automatic drive system
Top Climbing Grade 20% Voltage Reducer 30 A, 72 V to 12 V reducer
included
Warranty One year bumper-to-bumper warranty, less wear items; two year Trojan battery war-
ranty, based on date code

5
Functions
Power key: Controls the power supply of the whole vehicle. When the key is inserted
into it and turned clockwise, it will switch on the lights, horn, and the control sys-
tem; when the key is turned back, the power will be switched o.
Acceleration pedal: Controls the speed. It should be depressed slowly. The vehicle
speeds up with the gradual stepping-down, and reaches the full speed when the
pedal is stepped to the bottom. The 4
vehicle slows down when the pedal is released gradually. When the pedal is fully
released, electric brake works.
Service brake pedal: Decelerate the vehicle.
F/R switch: This switch is a three-position button. Depressing the upper part (F)
makes the vehicle move forwards while depressing the lower part (R) makes the
vehicle move backwards, and the middle is neutral. NOTE: The buzzer will sound
when the lower part of this button is depressed to give warning to the people
around your electric vehicle.
Hand-brake lever: Parks and brakes the vehicle.
Steering wheel: Controls the driving direction.
Light switch: Controls light system, including turning signals and headlight (in-
cludes high beam and lower beam).
Wiper and horn switch: Controls the wiper and horn.
Emergency stop switch: Stops the power of the whole vehicle in case of emergency.
NOTE: Before you switch on the vehicle, always check the status of this switch to

6
make sure that it is in the OFF position.
Combination meter: This meter shows information including lights, speed, range,
hand brake, and battery power.
Operational Process
Starting the vehicle
1. Select F for Forward or R for Reverse from F/R Button.
2. Switch on power with key.
3. Release the handbrake lever.
4. Depress the acceleration pedal smoothly.
WARNING: If you switch on Power Key first before selecting Forward or Reverse on
F/R Button, the vehicle will not run.
Stopping the vehicle
1. Step Service Brake Pedal to decelerate the vehicle until it stops completely
and shi F/R button to Neutral position.
2. Engage the handbrake lever to park the vehicle.
3. Release the service brake.
4. Switch o all lights.
5. Switch o the power key and take out the key.
Charging
CAUTION: There are two dierent kinds of chargers for this vehicle. One is an exteri-
or charger and the other is a built-in (on-body) charger. Before you use the charger,
read the charger operation manual.

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• Explosive hydrogen gas is produced while battery is charged. Only charge
the battery in well-ventilated areas.
• Before using the charger, check if the battery charger you are using is cor-
rectly rated for your local AC electricity network.
• Do not disconnect the DC output cord from the battery receptacle when
the charger is ON, otherwise an arc could occur which may cause an ex-
plosion.
• Do not open the housing of the charger. Only a qualified electrician should
open the housing of the charger.
• The charger should be stored in safe and dry room with good ventilation.
The charger should be packed properly if not used for long time.
2: Safety
The driver should have a good knowledge of the operation system of the vehicle
and its features while following rules for safe operation. WARNING: Drive the vehi-
cle o streets unless it is allowed.
• The vehicle cannot be overloaded, or the motor will be damaged. An over-
loaded vehicle can lose control and its life will be shortened.
• Unqualified persons are prohibited to drive the vehicle.
• Make sure this vehicle runs in its rated climbing ability.
• Don’t overtake other vehicles at crossroads, in blind areas or in other dan-
gerous zones.
• Keep your entire body inside the vehicle, keep seated and holding on while
the vehicle is moving.
• Do not start the vehicle until all occupants are securely seated.
• Keep your hands on the steering wheel and your eyes on the path ahead.
• Always back out the vehicle slowly and watch the back carefully.
• Avoid starting and stopping suddenly.
• Avoid turning the vehicle too sharply at high speeds.
• Always drive slowly up and down slopes.
• Do not make any modification or addition which may aect the capacity
or safety.
• Do not allow children to play in the vehicle. Children should be seated be-
tween adults and protected while the vehicle is moving.

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3: Maintenance
Battery Maintenance
WARNING: Battery electrolyte is poisonous and dangerous, may cause severe
burns, injury, etc.. Always wear protective clothing, gloves, and goggles when han-
dling batteries, electrolyte, and charging your battery.
KEEP OUT OF REACH OF CHILDREN.
Cleaning
• The exterior of the battery, the connection wires and bolts should always
be kept clean and dry. When cleaning, make sure all vent caps are tightly
in place. Clean the battery top with a cloth or brush and solution of bak-
ing soda and water. When cleaning, do not allow any cleaning solution or
other foreign matter to get inside the battery. This should be done every
week.
• Clean battery terminals and the inside of cable clamps using a post and
clamp cleaner. Clean terminals will have a bright metallic shine. This
should be done whenever necessary.
• Reconnect the clamps to the terminals and thinly coat them with petro-
leum jelly (Vaseline) to prevent corrosion.
• WARNING: Before you disconnect any battery cable from any terminal on
the battery, always remove the power by disconnecting the main battery
cable from the controller.
• Checking the terminals and nuts: The connection of the battery should al-
ways be kept in good condition. Check every week on whether any battery
cable terminal or nut has become loose in order to prevent any damage to
terminals. Check the status of the battery cable weekly. A damaged bat-
tery cable should be replaced immediately.
• Foreign matter: Do not place any objects on the battery and do not con-
nect the positive pole to the negative pole. This may cause a short circuit
and sparking.
Recharging
• As long as you use the vehicle, regardless of how long you have used it,
the battery should be recharged fully on the same day. Any delay in re-
charging will negatively aect the battery. The lead-acid battery does not
develop a memory, so need not be fully discharged before recharging.

9
• If the vehicle is going to be kept unused for a long time, the battery should
be fully recharged first. Aer that, the battery should be fully recharged
every two weeks.
• When driving, the driver should always be aware of the drop level of the
battery power from the battery power meter. Any drop means the battery
power is diminishing. The driver can estimate the distance needed to be
taken, and recharge the battery at a proper time in case the vehicle cannot
get back to the recharging station in time for recharging.
• WARNING: Make sure the battery is recharged before the battery power
meter shows 20% power is le inside the battery. An over-discharged bat-
tery will have a very short service life and will make recharging diicult.
• WARNING: During recharge, the vehicle should be parked in a well-venti-
lated area with the fill caps tightly secured. Keep far away from any flame
and sparks to avoid any explosion or fire that could cause physical injury
or damage to the property.
• During recharge, if the vehicle had doors, keep the doors open. Li the seat
bottom to keep the battery compartment open to the air.
Watering
Flooded batteries need water. More importantly, watering must be done at the
right time and in the right amount or else the battery's performance and longev-
ity suers. Water should always be added aer fully charging the battery. Prior to
charging, there should be enough water to cover the plates. If the battery has been
discharged partially or fully, the water level should also be above the plates. Keep-
ing the water at the correct level aer a full charge will prevent having to worry
about the water level at a dierent state of charge.
It is recommended that batteries be checked once a month until you get a feel for
how oen you must water your batteries. Important things to remember:
• Do not let the plates get exposed to air. This will damage (corrode) the
plates.
• Do not fill past the water level in the filling well to the cap. This most likely
will cause the battery to overflow acid, consequently losing capacity and
causing corrosion.
• Do not use water with a high mineral content. Use distilled or de-ionized
water only.
WARNING: The electrolyte is a solution of acid and water so skin contact should be
avoided.

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Watering procedure
1. Open the vent caps and look inside the fill wells.
2. Check electrolyte level; the minimum level is at the top of the plates.
3. If necessary add just enough water to cover the plates at this time.
4. Put batteries on a complete charge before adding any additional water
(refer to the Charging section).
5. Once charging is completed, open the vent caps and look inside the fill
wells.
6. Add water until the electrolyte level is 1/8" below the bottom of the fill
well.
7. A piece of rubber can be used safely to help determine this level.
8. Clean, replace, and tighten all vent caps.
CAUTION: Never add acid to a battery.
Testing: Visual inspection alone is not suicient to determine the overall health of
the battery. Both open-circuit voltage and specific gravity readings can give a good
indication of the battery's charge level, age, and health. Routine voltage and gravi-
ty checks will not only show the state of charge but also help spot signs of improper
maintenance, such as undercharging and over-watering, and possibly even locate
a bad or weak battery. The following steps outline how to properly perform routine
voltage and specific gravity testing on batteries.
Specific Gravity Test (Flooded batteries only)
1. Do not add water at this time.
2. Fill and drain the hydrometer 2 to 4 times before pulling out a sample.
3. There should be enough sample electrolyte in the hydrometer to com-
pletely support the float.
4. Take a reading, record it, and return the electrolyte back to the cell.
5. To check another cell, repeat the 3 steps above.
6. Check all cells in the battery.
7. Replace the vent caps and wipe o any electrolyte that might have been
spilled.
8. Correct the readings to 80° F:
• Add .004 to readings for every 10° above 80° F.
• Subtract .004 for every 10° below 80° F.
9. Compare the readings.
10. Check the state of charge using the table below.
If any specific gravity readings register low then follow the steps below.

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1. Check voltage level(s).
2. Perform equalization charge. Refer to the Equalizing section for the proper
procedure.
3. Take specific gravity readings again.
If any specific gravity reading still registers lower than the factory specification of
1.277+/- .007 then one or more of the following conditions may exist:
1. The battery is old and approaching the end of its life.
2. The battery was le in a state of discharge too long.
3. Electrolyte was lost due to spillage or overflow.
4. A weak or bad cell is developing
5. Battery was watered excessively previous to testing.
Batteries in conditions 1 - 4 should be taken to a specialist for further evaluation or
retired from service.
Open-Circuit Voltage Test
For accurate voltage readings, batteries must remain idle (no charging, no dis-
charging) for at least 6 hrs, preferably 24 hrs.
1. Disconnect all loads from the batteries.
2. Measure the voltage using a DC voltmeter.
3. Check the state of charge with the table below.
4. Charge the battery if it registers 0% to 70% charged.
If battery registers below the Table 1 values, the following conditions may exist:
• The battery was le in a state of discharge too long.
• The battery has a bad cell.
Batteries in these conditions should be taken to a specialist for further evaluation
or retired from service.

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Percentage of
Charge
Specific Gravity
Corrected to 80° F
Open circuit voltage
6 V 8 V 12 V 24 V 36 V 48 V
100% 1.277 6.37 8.49 12.73 25.46 38.20 50.93
90% 1.258 6.31 8.41 12.62 25.24 37.85 50.47
80% 1.238 6.25 8.33 12.50 25.00 37.49 49.99
70% 1.217 6.19 8.25 12.37 24.74 37.12 49.49
60% 1.195 6.12 8.16 12.24 24.48 36.72 48.96
50% 1.172 6.05 8.07 12.10 24.20 36.31 48.41
40% 1.148 5.98 7.97 11.96 23.92 35.87 47.83
30% 1.124 5.91 7.88 11.81 23.63 35.44 47.26
20% 1.098 5.83 7.77 11.66 23.32 34.97 46.63
10% 1.073 5.75 7.67 11.51 23.02 34.52 46.03
State of charge as related to specific gravity and open circuit voltage
Battery Installation
Tighten the battery cables to battery terminals with torque of 95 - 105 lbs. in. (10.7
- 11.9 N.M.) Make sure there is nothing else between the battery cable lug and
battery terminal post.
WARNING: When working with the battery, DO NOT put wrenches or any other
metal objects across the battery terminals, otherwise, an arc can occur, and it may
cause explosion of the battery and physical injury.
Battery should be installed or replaced only by a qualified electrician.
Traction/Motor Maintenance
The motor is designed for use up to 4000 feet above sea level and in a temperature
between -15° F and 105° F.
Never keep the motor running idly. Any mud, sand, and other clinging objects
should be cleaned away.
Check the carbon brush every three months. To change a worn or weakened car-
bon brush, press spring.
Troubleshooting for Motor (DC Motor only)
Warning: Only a qualified electrician should change and adjust the carbon brush.

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Symptoms Possible Causes
All copper plates turn black The pressure of brush is incorrect.
The commutator turns black in a
certain order and in groups
Short circuit in the commutator or armature coil; poor welding or
disconnection between the commutators and the armature coil.
The commutator turns black The central line of the commutator deviates or its surface is not
round and smooth.
The brush wears out, turns colors and
become broken
The motor vibrates; the clearance between the brush and its holder
is too big; the clearance between the brush and commutators is
too big; the mica between dierent commutators extrudes; the
brush is made by wrong materials; the brush is the wrong type.
Big sparks
The motor is overloaded; the commutators are not clean, round
or smooth; mica or some commutators extrude; the brush is not
ground properly; the brush is the wrong type; the brush is jammed
in the brush holder; the brush holder become loose or vibrating;
the polarity and sequence of magnetic poles is wrong.
The brush and its wires get hot Big sparks of the brush; poor contact between brush and so wires.
The brush is noisy The surface of the commutators is not smooth.
Speed Controller
Speed Controller Maintenance
The speed controller of the vehicle is wholly imported, which adopts high frequen-
cy MOS technology to realize the control of speed, torque and brake with smooth-
ness, silence, and high energy eiciency.
When the vehicle starts, the controller will inspect signals from the accelerator.
If signal exceeds 20%, the HPD (protection unit in the controller) will prohibit the
output of the controller. The controller will self-check when the vehicle is running.
If any defect inspected, the controller will stop the vehicle to protect the operator
and the vehicle.
Brake System Maintenance
Depress the brake pedal with a force of 65 lbs. The pedal travel shouldn’t exceed
2/3 of the full free pedal travel.
The clearance for the brake plate is self-adjusted. Under a force of around 45 lbs,
the parking brake handle should be fixed in one gear from 5 to 10 ratchets. When
the brake handle is released completely, the brake function will stop. Inspect and
change brake shoe, and add lubrication into the brake bearing periodically.

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Lubrication
Use 901 vehicle brake oil DOT3 as brake oil. Use 1L of 85W/90GL lubrication oil
for gear box. Use 1L of 90GL hypoid gear oil for the rear axle. Lubrication points:
steering gears, horizontal bars, steering ball joints, and bearings.
General Maintenance Notes
• To avoid any damage on the brake shoe, the handbrake should be re-
leased to its bottom before staring the vehicle.
• The lubricant for rear power assembly must be applied and changed as
per user’s manual.
• The brake system must be adjusted once every 3 months.
• The electricity system must be checked once every 3 months (especially
main circuit) for its fastening parts and wiring connections. Meanwhile
the contactor should be checked. Any defective parts should be replaced
immediately. Dust should be cleaned with low pressure air.
• The electric contactors easily become hot if their mutual contact is not
in good condition, so special attention should be paid regularly to the
electric contactors.
• When changing a fuse, make sure that the new fuse is right in rated cur-
rent.
• Disconnect the positive pole from the battery when maintenance is done.
• Never step the accelerator hard and frequently, which may shorten the
life of the controller.
• It is prohibited to pour any other liquids (such as battery additives, min-
eral water and tap water) into the battery. Only distilled water should fill
battery.
•
Periodic Maintenance
• Check if the contact between contacting points of the contactor is in good
condition, check for any mechanical sticking or jamming.
• Check if the micro switch in the accelerator can be switched on and o
properly.
• Check if the switch for the turn signal can be switched on and o proper-
ly.

15
• Check if all the connections between the motor, the battery, and the con-
troller are in good condition.
Use the following cleaning procedure for routine maintenance:
1. Turn the power key to OFF position.
2. Remove power by disconnecting the battery.
3. Discharge the capacitors in the controller by connecting a load (such as a
contactor coil or a horn) across the controller’s B+ and B- terminals.
4. Remove any dirt or corrosion from the connector areas. The controller
should be wiped clean with moist rag. Dry it before reconnecting the bat-
tery. The controller should not be subjected to pressured water flow from
either a standard hose or a power washer.
5. Make sure the connections are tight, but do not over-tighten them.
NOTE: All above checks should be performed with the power o. Above checks
shall be carried out once every 3 months; aer the power is turned o, the
wave-filter capacitor in the controller unit should continue discharging for a few
minutes more; don’t wash the electrical parts with water. You can remove dust
with a brush or high–pressure air.
Periodic Maintenance Chart
WARNING: Make sure to turn o the power key and apply the park brake when
you do the maintenance unless specified.
Item Descriptions Daily Weekly Monthly Quarterly Annually
Battery
Check the liquid level. Add distilled
water if necessary. ☑
Charge the battery. ☑
Tighten the nut on the battery
cable. ☑
Check if the battery is over-dis-
charged (the battery power meter
flashing).
☑
Check the liquid density of the
battery; standard density should be
1.275±0.005.
☑
Check if the battery is charged fully
by using the hydrometer and check-
ing the battery power meter.
☑
Clean the surface of battery. ☑

16
Item Descriptions Daily Weekly Monthly Quarterly Annually
Charger
Observe the charging status, check
if the charger plug becomes hot. ☑
Clean the surface of the charger. Do
not get any water inside the charger. ☑
Controller
Check if all terminals are tightened
properly. Do this aer the power
is o.
☑
Clean the surface of the controller. ☑
Check if the solenoid is in order,
checking its touching point. ☑
Motor
Check if any water gets in. Check if it
becomes too hot. ☑
Check if the carbon brush should be
replaced. (DC motor only) ☑
Check if the accelerator pedal works
well and if it can be released freely
and automatically.
☑
Chassis and
body
Check if the brake drum and shoe. ☑
Check if the hand brake functions. ☑
Check if the hose and tube for the
brake liquid leaking. ☑
Check if the brake liquid inside the
brake liquid tank is enough. ☑
Check the air pressure inside the
tire, check if the tire surface is worn,
and check if the nuts are tightened
properly.
☑
Check if the shock absorber has any
oil leaking, flat or abnormal noise. ☑
Check if there is oil leaking on the
gear box and the rear end. ☑
Add the lubricant inside the wheel
hub, steering system. ☑
Adjust the toe-in of the front end. ☑
Clean the body and seat. ☑

17
4: Storage
Follow the steps below when the vehicle is stored.
1. Check the liquid level inside the battery; recharge it fully before storing
the vehicle. WARNING: Charge the battery once a month if your vehicle
will be stored more than one month.
2. Turn the power key to OFF position, remove the key, and store the key in
a safe place.
3. Engage the handbrake.
4. Check the tire pressure to make sure its pressure is set to recommended
pressure.
5. Clean the exterior of the vehicle and apply a rust inhibitor.
6. Cover the vehicle with a breathable cover and store it in a dry, safe, and
well-ventilated place.
7. If you plan to store the vehicle for a longer time, check the liquid level
inside the battery and recharge the battery monthly.
5: Troubleshooting
There is no settled mode to diagnose and eliminate malfunctions. During main-
taining and checking, we suggest you first listen, then look and feel. Below is the
diagnoses and maintenance of some common malfunctions.
1. The vehicle doesn't move aer turning on the power key and stepping on accelerator pedal.
Malfunction Possible Reason Troubleshooting
Turn on power key,
voltmeter has no signal
Connector(s) in circuit is loose or open Tighten or connect
Fuse of controller or main circuit is open Change fuse
Battery cable(s) is loose or disconnected Tighten of change
Power key is broken Change
Voltmeter is broken Change
Battery terminals connect improperly Adjust
Turn on power key,
voltmeter has signal
Improper operating procedure Operate properly
Controller failure Check or change
Solenoid failure Check, repair, change
Accelerator failure Repair or change
Motor failure Repair or change
Parking brake doesn’t loosen Loosen parking brake
Over-heat protection Check, eliminate

18
2. Locking control when vehicle starts running, speed cannot be adjusted.
Malfunction Possible Reason Troubleshooting
Vehicle runs at full speed
when it starts
Terminals of solenoid stick together Check or repair
Controller failure Change
Potentiometer failure Repair or change
Vehicle stops immediately
aer it starts
Internal short of motor Repair or change
Motor is assembled too tight or blocked Repair or change
Controller failure Repair or change
Accelerator failure Repair or change
Normal power at low
speed, weak power at high
speed
Controller failure Check or change
Motor failure Check or change
Accelerator failure Check or change
3. Vehicle cannot change direction, only runs in one direction.
Malfunction Possible Reason Troubleshooting
Only runs in one direction F&R switch failure Change
Controller Failure Change
4. Possible reason and troubleshooting for malfunctions of mechanic system.
System Malfunction Possible Reason Troubleshooting
Transmission
system
Abnormal sound when
running
Clearance of rear axle decelerating
gear is too big, or the decelerating gear
is broken
Adjust, change
Transmission cross sha is worn out Change
Gear of transmission is worn out or
damaged Change
Flange bearing is damaged Change
Motor bearing is damaged Change
Gear liquid is deficient or empty Add gear liquid
Hard to shi gear, and/
or gear shi jumps in
dierent positions
Clutch cannot separate smoothly Adjust
Gear shi wire is damaged Change
Gear inside transmission case is worn
out Change
Orientation pin is loose Change
Steering system Steering heavy
Pressure of front tire is deficient Check the pres-
sure and inflate
Screw plug of redirector is too tight Adjust
Lack of lube in redirector Maintain/add
lube
Toe-in is abnormal Adjust

19
4. Possible reason and troubleshooting for malfunctions of mechanic system.
System Malfunction Possible Reason Troubleshooting
Steering
system
Steering heavy
Clearance of tension rod ball is too big Change
Steering knuckle and master pin is not lubri-
cated Add lube
Steering sha or its plastic cover is worn out Change
Unstable wheels
Rack of redirector is worn out Change redirector
Screw plug of redirector is too tight Adjust
Toe-in is adjusted improperly Adjust
Bearing of front wheel is worn out Change
Tie rod ball and joint is worn out Change tie rod
Redirector is loose Tighten
Driving
system
Deflected running
The pressure of the two front tires is dierent Inflate
Toe-in is too big or too small Adjust
Tightness of the le and right drum bearing of
front wheels is dierent Adjust
Brake of one wheel is too tight Adjust or change
Spring shock absorber is abnormal Change
Front suspension is loose Change
Abnormal tire fray
Tire pressure is abnormal Inflate
Toe-in is improper Adjust
Drum bearing loose Change
U type bolt of leaf spring is loose Tighten
Rim is distorted or frame is distorted Tighten
Brake force of each wheel is dierent Adjust
Overexerting accelerate or braking frequently Alter operation
Brake system
Brake fail
Master cylinder and/or wheel cylinder is dam-
aged or leaking oil
Check, eliminate,
change
Brake fluid is insuicient or empty Add fluid
Air enters into oil pipe Let air out
Free travel of brake pedal is too long or the
clearance of arrester is too big Adjust
Brake drum is worn out or distorted Change
Master cylinder leaks oil internally Change
Braking deviation
The clearance of le brake drum shoe and right
brake drum shoe is dierent Adjust
Oil is on one arrester’s brake shoe Dispose/change
Tire pressures are dierent Repair/change
One wheel cylinder’s piston is blocked Adjust
Wheels are aligned improperly Adjust
Brake drum becomes out of round Change

20
4. Possible reason and troubleshooting for malfunctions of mechanic system.
System Malfunction Possible Reason Troubleshooting
Brake system
Braking drag
Brake pedal has no free travel Adjust
Clearance between brake shoe and drum is too
small or releasing spring is disabled Adjust or change
Piston of wheel cylinder is ineective Check or change
Piston of master cylinder is ineective Change spring
Parking brake is ineective Change spring
Braking noise
Shoes distort Change
Brake facing wear out Change
Brake drum breach, scraped to uneven Change