transistors

http://fourier.eng.hmc.edu/e84/lectures/figures/transistorBJT1.gif

the transistor has three points,the base
the emmiter and collector.
the voltage of the emmiter is higher than that of the collector when measured

the above is two diodes i tied cathode to cathode to form a P-N-P transistor

to test transistors set the multi-meter to the diode test. a transistor is pretty much two diodes connected together anode to anode N-P-N or cathode P-N-P to cathode.so once you have established the common connection you can determine which is collector(lower voltage) and emitter(higher voltage).

Starter On car

i began by de-activating the igntion system to prevent the starter from engaging.
then i removed any surface charge that may have been on the battery by switching on the headlights to take it off.
while cranking, i checked the available voltage at the battery terminals:

Cranking voltage spec: 9.6volts

Cranking voltage 11.47 volt

which was a pass.

1. Check loss between battery positive post and solenoid starter input stud while cranking.

Spec less than 0.20 volts, Volts drop 0.18 V1 Pass 

2. Check loss across solenoid main input and output terminal studs while cranking.

Spec less than 0.10 volts, Volts drop 0.07 V2 Pass 

3. Check loss between battery negative and starter motor body while cranking.

Spec less than 0.20 volts, Volts drop 0.01 V3 Pass 

4. Add all the voltages drops together to find maximum voltage drop.

Maximum Allowed 0.50 volts, Total volts drop 0.26Volts Pass 

below are the given instructions for the measuring the current draw of the motor.  if the reading is above specification this could indicate resistance along the circuit

1. Set the meter on 400 amps DC and push the Zero Button to zero the meter, if the reading doesn’t Zero push the Hold Button and repeat the procedure.

2. Once the meter is Zeroed clamp the pick up around the positive battery lead anywhere between the positive terminal and the “B” terminal of the solenoid.

3. Have someone crank the engine and as it is cranking push the hold button, this will retain your reading.

Starter current draw: 103.2 amps. Pass 

starter off car

this assignment required me to disassemble a starter motor and test its components to check their working condition andto dismantle a starter we were given the below to follow in sequence:

1. Scribe alignment marks along the two end housings and field housings (main body) of the starter motor, this will help to align the major components.

2. Remove M terminal wire from the solenoid (this wire connects the output from the solenoid to the starter motor)

3. Scribe alignment marks on the solenoid body and mounting then remove solenoid

4. Remove any screws in the commutator end housing (failure to do this can result in major damage to the brushes or field windings).

5. Remove commutator end housing

6. Remove brushes as necessary to remove brush plate assembly

7. Remove field coil housing (main body of the starter motor).

8. Remove shift fork from drive end housing (it is important that you mark the position of the shift fork).

9. Remove the armature assembly

10. Remove the overrunning clutch from the shaft (clean any burrs with emery paper for easy removal of the clutch)
    
    

    
    

    the next test was the Armature ground test. this is done to establish whether there is a short in the insulation which,if there is, would compromise the armature's magnetic field ,reducing or impairing the performance.If this be the case the armature would need replacement. To do this,on your multimeter select the Ohms(unit of resistance) range and
    and with the multimeter probes check between each of the commutator sections and the armature core. 
    MANUFACTURE SPECIFICATION:Infinity
    TEST RESULT: 1 (on my multimeter this is equivalent)

    
    

    
    

    
    

    next is the continuity circuit test. this is testing the resistance of the commutator,which should be none or low,since it makes contact with the brushes feeding electricity to the windings. if there is high resistance this would affect the function of the armature as the motor would not turn and the starter motor would not work.the armature would have to be replaced.With the Ohmmeter in the same range check continuity between one of the commutator segments while moving the second probe around on each of the other commutator segments.

     

    MANUFACTURER SPEC    :0 - 1 Ω
    TEST RESULT: Pass
    

    
    

    
    

    Next was measuring the diameter of the commutator with Venier calipers. if the diameter was too small it would make bad contact with the brushes affecting the continuity which inturn would cause bad performance, the armature would have to be replaced.

    the mica undercut is to make sure there is enough space between segments and prevent shorting in the circuit and ensure there is good contact with the brushes.

    MANUFACTURER SPEC:26.8mm – 31mm

    TEST RESULT: 30mm.....pass
    
    
    MICA UNDERCUT SPEC:0.7mm – 1.0mm
    TEST RESULT: 0.8mm....pass
    

    
    

    
    

    the armature shaft runout test is to check how much runout there is on the armature. if there is too much runout, it would cause poling or damage to the core or winding as it spins.To check for run-out, place the armature between the “V” blocks.Turn the armature 360° while reading the dial test indicator set up on the armature core.

    MANUFACTURER SPEC:0mm – 0.2mm

    TEST RESULTS:0.03 mm.....pass
    

    
    

    
    

    
    

    the next test i performed was on the growler machince. to do this,

    1. Place the armature on the “V” of the growler.

    
    

    2. Turn the switch on to Growler position.

    
    

    3. Hold a hacksaw blade or metal strip along the armature and rotate the armature.

    
    

    if the hacksaw vibrated it indicated an internal short in the armature core.this means there is damage in windings insulation and the current is not passing through it.

    When i perfomed this test the hacksaw did not vibrate indicating no short therefore the component passed

    
    

    
    

    Next test i did was for Continuity in the Field Windings..depending on the design of the motor, the windings maybe or maynot be grounded. This particular one was not grounded  With the meter in the Ohms range, place the probes on the windings and get the reading. There shouldn't be too much resistance as this would interfere with the magnetic field and the coils would need replacement.

    MANUFACTURERS SPEC:0 – 0.02Ω

    TEST RESULT: 0
    
    
    If the windings are grounded,this particular test would not apply. In that case the black probe of the multimeter would need to be on the starter motor body and any reading would indicate a fault.
    
    
    Measure the length of the brushes and a visual inspection was next.the inspection is for wear and tear and cracks.if the brushes are too short,they would have bad contact with the commutator and this would short the circuit and drain the battery without any motion occurring.
    MANUFACTURES SPEC: 5mm(new brushes 14mm)
    TEST RESULT: average of 13.6 mm...pass
    
    
    Then i tested the grounded insulated brushes for short circuit. this required the Ohm meter set on the lowest resistance and an open circuit result should be obtained. If not, the brush holder would need replacement as this means the commutator and armature wont get enough voltage, resulting in a bad performing starter.
    INSULATED BRUSH HOLDER
    MANUFACTURERS SPEC: infinity
    TEST RESULTS: 1(equivalent of my meter)
    
    
    The nest test was that of the solenoid,to check the pull in winding.this test checks the resistance or lack of it in the winding connections.this is done with a low voltage for five seconds to prevent heat damage.to do this i connected the battery supply terminal "s" and starter motor supply in"m" to a 9v power supply(Load tester). The amp draw was within spec. and the plunger was pulled in.
    
    
    Next was the hold in test which establishes whether it can actually hold in the plunger and shows if the windings  have enough resistance,too much or too little could affect the plungers action.too much and the plunger is held in longer than its supposed to by the created magnetic field and too little it would not e enough to hold it in.
    To do this test, connected a power supply between the "s"terminal and the solenoid body.with my finger i pushed in the plunger and thenn applied the power. effectively the plunger should stay pulled in without me holding it in and it did.
    
    The final test was a visual inspection of the pinion gear, bushes and clutch. the pinion gear check was for damage and smooth movement along the armature shaft and it was good by turning the pinion gear in the direction of motor rotation, the clutch should free wheel and against direct of rotation it should lock.
    The bushes i checked for wear and tear which was very minimum and the clearance into the end housing.
    After completing this tests i was ready to assemble the motor back together.The motor should run as before disassembling or  better if repairs were needed,in my case none and it was in good working condition. 
    
    
    
    
    
    
    
    
    

    
    

    
    

    
    
    
    
    
    

flash codes

i used my toyota cynos 1991 for this practical and my tutor provided the manual with the flash codes. my tutor created a fault in the engine and using the check engine light flashes as an indicator i was to find the problem and fix it. the check engine light should remain on when the car is turned on and engine not running.
once engine is started and the check engine light remains on, the diagnosis system has detected and error in the system.
I opened the diagnostic plug located under the bonnet and jumped/bridged terminals E1 and TE1. Using the table below as reference, the fault code was 31( the check light flashed 3 times then 1 time).this means the was an error in the vacuum sensor circuit.My tutor had unplugged it. i pushed it back in and cleared the fault code by disconnecting the battery negative terminal for half a minute. The check engine light did not come on so i had diagnosed the fault.

Diagnostic Fault Codes

Fault Code	Item
1	Normal
2	Vacuum Sensor Signal
3	Ignition Signal
4	Water Temperature Signal
6	RPM Signal
7	Throttle Position Sensor
8	Intake Air Temperature
9	Vehicle Speed Sensor
10	Starter Signal
11	Air Conditioner Switch
12	G, NE Signal Circuit
13	NE Signal Circuit
14	Ignition Circuit
16	ECT Control Signal
21	Oxygen Sensor Circuit
22	Water Temperature Circuit
24	Intake Air Temperature Circuit
25	Air – Fuel Ratio Lean Malfunction
31	Vacuum Sensor Circuit
33	Idle Speed Control System
41	Throttle Position Sensor Circuit

transmission(manual front wheel and automatic)

A manual transmission allow the vehicles driver to operate at the engines most efficient speed range.using a gear lever,the driver can select the suitable engine torque, i.e a lower gear for increase load requirement or higher gear for less or higher speed ranges as well as neutral to disengage drive and a reverse gear. the gear shafts have bearings on each end to support and ensure free movement of the parts. 

the transmission parts are lubricated at all times as high friction occurs when operating.the viscosity changes depending on the engine type or manufacturer specs.

 above is the reverse-idler gear which is a straight-tooth spur gear type.when engaged by the countershaft reverse gear, this gear reverses the motion of the drives rotation in this case the ring gear for a front wheel drive

above is the open gear box, 5 speed i.e it has five drive gears plus a reverse gear which i had taken out.this came out of a front wheel drive so the output shaft drives the ring gear which makes up the transaxle.

the gear type is helical.these are strong and durable aswell as quiet with a moderate cost so they are the preferred type of most manufacturers.

 i pulled out the input and output shaft as above, and counted the teeth of the gears to find the torque ratio of the gears(numerical speed ratio). the formula for finding gear ratio is driven gear teeth divided by driving gear teeth, the answer being driven:driving

1st gear         39/11=  3.55:1
2nd gear        40/21=  1.904:1
3rd gear        38/29=  1.310:1
4th gear         32/33=  0.097:1
5th gear         31/38=  0.82:1

 the above side view of the ring gear shows the differential. In a front wheel drive it is intergrated into the gear box,a section referred to as the transaxle. the differential distributes the torque threeways, that if from the ring gears rotation through the differential both sides of the drive shafts rotate, turning the wheels.

below are the selector rails with their shift forks.the gear lever/gear stick controls the selection of the gears with the use of rod cables or direct coupling with the selector rails or rods which inturn move the selector forks,they are attached to the rails by lock pins or bolts

AUTOMATIC TRANSMISSION

the gears are shifted automatically depending on the load requirement and or vehicle speed.its consists of a torque converter,hydraulic system and mechanical gear ratio and operating system.

Torque convertor.