Starter Motor Bench Testing and Repair

Remove over Safety & Resource
Student must wear overalls and steel cap work boots at all times

Resources:
Starter motor test bench, 6-12 volt power supply, digital voltmeter, amature growler, 45 volt test light, Suitable tolls and equipment to enable starter motors to be dismantled and repaired, preengaged starter motor, manufacturers specification if possible.




This is the test and measurements taken to perform on the Starter Motor.

First we start with:

• No Load Test
• We test No Load Voltage
• Test No Load current

Manufacturers Specifications

• No Less that 11 Volts
• 30-50 Amps
• Results
• 11.5 Volts
• Nil

 To Disassemble the Starter Motor I have included the following steps:

• Mark along two end housing, it helps when you assemble component
• Remove M Terminal wire from Solenoid
• Remove the Solenoid
• Remove commutator end house (and failure in the major damage to the brush or field winding)
• Remove brushes and brush plate
• Remove field coil housing
• Remove shift fork
• Remove armuature
• Remove over running clutch

Visual

• Crack
• overheating
• Burning
• Physical Damage in coil winding
• poling

All Visual Inspection had passed

- We performed Ground Circuit Test
- We used multimeter to test commutator segment and the armature core on armature ground and the results O (zero) and it is serviceable.
- We did a test on continuity circuit on Ohmeter to check continuity between commutator segments and probe the around on each while moving and results come 0.5ohm and it is serviceable.
- Commutator Measure to check the mica undercut depth.  We use the Vernier Caliper to measure this.
- These are the manufactures specifications

• minimum diameter - 26.8mm-31mm
• mica undercut - 0.7mm-1.0mm

The Results
30mm - minimum diameter - yes it is serviceable
1.0mm - mica undercut - yes it is serviceable



BRUSHES
The brushes are removed from the Starter Motor and measured according to the Manufacturers Specification requirements.   If the bruchess ready under 5mm they will need to be replaced.
Findings:

• 14mm
• 16mm

CAR STARTER MOTOR CIRCUIT ASSESSMENT
The vehicle we have used on this assessment is a Nissan Sentra 1992

1. We inspect the vehicle to ensure there are no damages i.e loose wiring
2. Check if the vehicle is a Manual or Automatic
3. Check if the vehicle is equpiied with a power source device

PRELIMNARY CHECK BEFORE CARRYING CIRCUIT VOLTAGE DROP

1. De-activate ignition and fuel injection system
2. Checked the battery for service ability
3. selected the right range on the meter

CHECK BATTERY AVAILALE VOLTAGE UNDER CRANKING RESULT ON CRANKING VOLTAGE- 10.8V

1. Voltage drop positive side of the circuit
2. spec less than = 0.20volts > volt drop=0.06
3. voltage drop on Solenoid
4. Spec less than = 0.10volts > volt drop = 0.10
5. Votage drop onearth side of the circuits

Spec kess = 0.20v > volts drop 0.12
Maximum allowed = 0.50 > Total volts drop 0.28
Specification = 125 > 150amps
Starter Draw = 079.9

All the reading and checking we have performed on the vehicle circuit was inside of the specification reading and the circuit was in good condition.

CAPACITOR
Calulation on how fast the capacitor should charge.

1. The following calculations are used to determine how fast the capacitor can charge i.e Calculated time, seconds and Capacitance UF into Resistance x5 to get the calculations.

CAPACITANCE	CAPACITANCE	X	RESISTANCE	X	5	CALCULATED
(µf)	(F)		Ω			TIME
						Seconds
10	0.00001	x	1,000	X	5	0.05
1	0.000001	x	250,000	X	5	1,250
100	0.0001	x	10,000	X	5	0.005
300	0.0003	x	4,500	X	5	6.75

                                                      

CALCULATE RESISTOR SIZE
The follwing calculations are done on four resistors, to determine this we check the number of resistors or the UF and then find the identifcation x5 to find determine the answer.  e.g:

CAPACITANCE	CAPACITANCE	X	5	Answer
(µf)	(F)
22	0.000022	X	5	0.00011
100	0.001	X	5	5
0.47	0.0000004	X	5	0.000002
22	0.000022	X	5	0.00011

MONITORING CAPACITOR CHARGE TIME VERSE VOLTAGE
First we bridge the wire and then remove the bridge to count every 10 second up to 220 seconds in 3.7minutes to see the charge.  The following is readings:

10	90	20	1.79	30	2.77
40	3.74	50	4.45	60	5.69
70	6.57	80	7.24	90	7.8
100	8.4	110	80.82	120	9.2
130	9.6	140	9.9	150	10.15
160	10.4	170	10.6	180	10.8
190	10.99	200	11.15	210	11.32

LOGIC PROB LED TESTER LIGHT

The following is instructions and equipment/materials to make the Probe

Equipment:

• Bass Rod
• Red Lead
• Green Lead
• Black Wire
• Red Wire
• 2,1000 ohms resistors
• Red/Black Alligator Clips
• 100mm Plastic tube
• Heat Shrink of 3 different sizes
• Red & Black Rubber to convert the wires

Instructions

1. First we took the wire and stripped both ends
2. Then we soldered the resistor to the wire
3. We soldered the Red Lead to the wire
4. We then soldered the Green Lead to the wire
5. After that I granted the both end of brass and the middle
6. I soldered the Green & Red Lead together on brass
7. Use the black rubber to cover the brass and wire together and then I used the heat gun to to shrink the rubber so we can wrap it all together.

Reflection:

This lesson was good for me, it showed me the importance of Prob Lead testing for off short circuit in Electrical systems and also gave me new ideas on how it can be used.

BATTERY TESTING

This area talks about how to test & check a battery and if it is need for a service or if it needs replacement.

• First is Visual Check
• Checking if any unsafe or any terminal needs to be cleaned or replaced
• Checking if any signs of swelling can cause over charging
• Checking level of Acid or H2S04 if it is on the correct level

Testing specific gravity & the reading before you top up the Cells

You use hydrometer tester

• Cell 1 = reading > 1125 = Red
• Cell 2 = reading > 1275 = Green
• Cell 3 = reading > NO READING
• Cell 4 = reading > 1300 = Green
• Cell 5 = reading > NO READING
• Cell 6 = reading > 1300 > Clear

The battery Gravity failed, this means the battery needs to be replaced.

Testing a Open Circuit Tester

1. Removing Surface Charge
2. When the battery is fully charged, you will need to remove the surface charged and turn on the headlight or anything that draws power away from the alternator. 

Use the volts meter to measure the results with 12.65v 

• 100% > 12.7v
• 95% > 12.6v
• 75% > 12.5v
• 50% > 12.4v
• 25% > 12.2v

The measure of state of charged was 75% > 12.5v

• The battery  is always charged slowly or short fast bursts
• To clean any surface on top the battery like acid or HzSo4
• Use hot water and the baking soda to clean
• Use vaseline to crease the terminals

• To check if the battery needs to be recharged or replaced
• The reading of recharged is = 50% > 12.4v
• The reading of replacing the battery is = 25% > 12.2v

ALTERNATOR ON THE ENGINE TESTING AT SCHOOL

• First Visual checking of the belt
• See if the belt tension is Good
• Check if Belt is cracked or needs replacement
• Mounting of Alternator if not loose

Belt was worn out and needed replacement and was found to have no oil on the belt.

ELECTRICITY CIRCUITS

AVAILABLE VOLTAGE

Using a voltmeter I measured the available voltage and these are my findings:

• The Positive 12v Supply (B+) = 12 Volt
• Terminal before the switch = 12 volt
• Terminal after the switch = 12 volt
• Terminal before the light bulb = 12.5 Volt
• Terminal after the light bulb = 0 Volt
• The negative on the 12v supply (N-) = 0 volt

While the voltage progressess through different components of the circuit you can clearly see that the voltage gets less as it gets used up pushing through the resistance.

VOLTAGE DROP
Again I used the volmeter to measure the voltae drop across the different components of the circuit and my findings are below:

• From the B+ of the 12v supply to the input of the switch = 0.07v
• From the input of the switch to the output of the switch = 0.03v
• From the output of the switch to the input of the bulb = 0.03v
• From the input of the bulb to thye output of the bulb = 12.78v
• From the output of the bulb  to the N- of the 12v supply 0.1v

A voltage drop in an electrical circuit normally occurs when current is passed through the wire. The greater the resistance of the circuit, the higher the voltage drop. The largest voltage drop in my finding are from the input of the bulb to the output of the bulb, the reason for this is because when there is more voltage there is more resistance.

MEASURING AMPS IN A CIRCUIT
Using a amp meter I measure the amps  at different parts of the circuit, my findings are below:

• Wire before the switch = 0.33 amp
• Wire before light bult 1 = 0.33 amp
• Wire between light bulb 1 & 2 = 0.33 amp
• Wire between light bulb 2 & 3 = 0.33amp
• Wire after light bulb 3 = 0.33 amp

The measurement on the circuit is showing the same reading because the same amount of amp is going through the circuit.

4841 Electrcal

SAFETY FIRST

Here are a few hazards that we can find in a workshop and some important safety aspects
that should always be in place.

CRUSHING

• When working on a vehicle, ensure to always use a Jack under the car to support. 
• Axle stand is used to support the car incase the car comes off the jack
• Big Log to support the car incase the Jack fails
• Ramp to ensure the car remains up

FIRE

• Ensure a fire extinguisher is in a accessible area while working with electrical equipment or flammable fluids i.e petrol
• Overalls should always be worn to protect you from any fuel spill or when touching hot engines.
• Ensure that there is no electrical overload, always be aware of dangers when repairing or modifying electrical wiring.
• do not allow naked flame when working on a vehicle

SCALDING

• Ensure the engine has cooled down before removing the radiator cap
• also be aware of other fluids when the vehicle has recently been running i.e engine oil, transmission fluid or power steering fluid.

THE BATTERY

• Always wear protective clothing or eyewear when working with batteries as they contact sulphuric acid,
• Never allow a naked flame or spark caused either electrically or by tools, the battery gives of hydrogen gas which his highly flammable.