Alternator
Models - Models AC5, 11AC, 15ACR, 17ACR, 18ACR, 23ACR, A115/45, A133/55, LR135-111, LR135-113, LR135-114 and LR150-160.
General
These are driven by the engine in the same manner as a D.C. Generator, namely, belt driven from the crankshaft pulley, but the advantage lies in their ability to provide higher maximum output at lower speeds, to cope with increased electrical load demanded by modern equipment and decreased road speeds owing to increased density of traffic, especially in built up areas. They are also much lighter in weight, output for output.
As opposed to the DC Generator in which the armature windings rotate inside a stationary field system, the alternator has a rotating field system inside a stationary generating winding. When the rotor rotates inside the stator, the output produced is alternating current (AC). This is unsuitable for charging the battery which requires direct current (DC), so it is rectified by means of diodes which convert it to uni-directional flow to the battery.
The alternator voltage output is maintained within close limits by means of a control box which is fully transistorised and functions as a fast switch.
Precautions
As previously described the diodes in the alternator function as one-way valves and the transistors in the regulator/control box operate as fast switches. Both are accurate and sensitive.
They do not wear out and cannot be adjusted, but because they are sensitive to voltage changes and high temperature, the precautions are vital to prevent them from being destroyed.
a) DO NOT disconnect the battery whilst the engine is running. This will cause a voltage surge in the alternator charging system that will immediately ruin the diodes or transistors.
b) DO NOT disconnect a lead without first stopping the engine and turning all electrical switches to the off position.
c) DO NOT cause a short circuit by connecting leads to incorrect terminals. Always identify a lead to its correct terminal. A short circuit or wrong connection giving reverse polarity will immediately and permanently ruin transistors or diodes.
d) DO NOT connect a battery into the system without checking for correct polarity and voltage.
e) DO NOT "flash" connections to check for current flow. No matter how brief the contact the transistors may be ruined.
Maintenance
The alternator charging system will normally require very little attention, but it should be kept free from build-up of dirt, and a check made if it fails to keep the battery charged.
a) Regularly inspect the driving belts for wear and correct tension. It is important to ensure that all belts on a multiple belt drive have equal tension and are each carrying their share of the load. Slack belts will wear rapidly and cause slip which will not drive the alternator at the required speed. Drive belts which are too tight impose severe side thrust on the alternator bearings and shorten their life. Periodically ensure that the alternator is correctly aligned to the drive.
b) Do not replace faulty belts individually in a multibelt system. A complete matched set of drive belts must always be used.
c) Keep the alternator clean with a cloth moistened in kerosene or cleaning fluids. Ensure that ventilation slots and air spaces are clear and unobstructed.
d) Remove any dirt accumulated on the regulator/control box housing, and ensure that cooling air can pass freely over the casing.
Fault Finding on AC5
The AC 5 alternator is so designed that a flow of current indicated either by the extinguishing of the warning light, or as shown on the ammeter, is sufficient evidence that the system is in proper working order. Therefore, no open circuit, voltage or current output checks should be performed on the installation UNLESS:-
a) The warning light fails to illuminate when the generator is stationary, and the switch is closed OR fails to become extinguished when the alternator is running.
b) No charging current is shown on ammeter.
c) The battery is flat.
d) The battery is "boiling", indicating loss of voltage control.
If any of the above symptoms occur, the procedure indicated below should be followed.
a) Connect a good quality moving coil voltmeter 0-50 volts range across the battery or regulator negative terminal, and one of the three positive terminals marked LO, MED, HI. Disconnect alternator output terminal. Fit a good quality moving coil 0 - 100 amp ammeter in series with the alternator terminal and output lead. The battery should be in a charged condition.
b) Close the warning light switch (master electric switch on dashboard) when the warning lamp should light up.
c) Switch on a 10-15 amperes load such as lights, fans, etc., for fifteen minutes.
- 1. The warning light should go out.
- 2. The ammeter records a small charge dependant on engine speed.
d) Start engine and run at fast idle speed when
e) Increase engine speed momentarily to maximum speed, when the charging current should be about 31 Amperes for 24 Volt, and 55 Amperes for 12 volt systems.
f) With the alternator running at approximately half speed, (engine speed about 1,500 rev/min) switch off electrical load. Depending on the connection selected for the positive sensing wire LO, MED or HI, the voltage should rise to between 26 and 28 volts on 24 volt systems and 13-14 volts on 12 volt systems and then remain constant. At the same time the current reading should drop appreciably.
Any variance in the above data could indicate a fault and the following procedure should be adopted before disconnecting any components.
The regulator is a sealed unit and is non-repairable and if found to be faulty it must be replaced.
Warning Lamp does not light up when switched "On".
Check the bulb.
If no fault
Check all wiring connections at regulator, alternator and battery.
If no fault
Switch off, disconnect 'F' lead at regulator and connect it to the negative terminal.
Switch on. If warning lamp lights up, the regulator is faulty. If lamp fails to light up, the alternator is faulty.
Warning Lamp does not go out and Ammeter shows no output when running.
Check all regulator, alternator and battery connections.
If no fault
Switch off, disconnect 'F' lead at regulator and connect to regulator negative terminal.
Switch on, and run at fast idle.
If no output, alternator is faulty.
If output appears, regulator is faulty.
Warning Lamp does not go out when running and Ammeter shows reduced output with full output only at maximum speed or Warning Lamp goes out but Alternator delivers reduced output. Full output only at maximum speed.
Alternator faulty. Remove from installation and apply open circuit diode check.
Warning Lamp flashes intermittently and Ammeter needle oscillates when Battery is fully charged and no loads are switched in.
Check for excessive resistance in regulator negative sensing lead.
If no fault, regulator is faulty.
Batteries overcharging and Ammeter indicates high or full output all the time.
Check regulator positive sensing lead and its connection at regulator.
If no fault, regulator is faulty.
Fault Finding on 11AC
If the alternator does not produce its rated output of 43 amperes for 12 volt and 23 amperes for 24 volt circuit, the failure may be due to any unit or the associated wiring, and the following procedure should be followed.
Test 1
Checking the Field Isolating Relay
Disconnect the earthed battery terminal and the cable from the alternator main output terminal. Connect a 0-60 DC ammeter between the terminal and disconnected cable. Link terminals 'C1' and 'C2' on the field relay. Reconnect the battery cable. Close the master switch and start engine and run at charging speed. If ammeter shows a charge the relay is faulty, or its wiring and connections.
If ammeter shows no charge, carry on with Test 2.
Test 2
Checking the Alternator and Control Box
Leave the test ammeter connected, and disconnect cables 'F' and '-' from control unit and join them together. Remove link from field relay terminals and ensure they are connected to 'C1' and 'C2'. Start engine and run at charging speed.
Ammeter should indicate current values of 35 amps or more for 12 volt circuit or 22 amps or more for 24 volt circuit. A zero or low reading indicates a faulty alternator.
If satisfactory output is recorded, a faulty control unit is indicated.
Test 3
Checking or Adjusting the Voltage Setting
The regulator of the 4 TR control unit must be set on CLOSED CIRCUIT, when the alternator is under load. Also, the system must be stabilised before checking or resetting is carried out, and the battery must be in a well charged condition. Check the battery to control unit wiring, to ensure that the resistance of the complete circuit does not exceed 0.1 ohm. Any high resistance must be traced and remedied. Connect a test DC voltmeter (suppressed zero type) scale 12-15 volts for 12 volt installations or 24-30 volts for 24 volt installations, between the battery terminals, and note the reading with no electrical load. Disconnect battery earth cable and connect test ammeter between alternator main terminal and disconnected cable. Reconnect battery earth cable, and switch on an electrical load of approximately two amps, such as, side and tall lights. Start engine and run at about 2000 rev/min for at least eight minutes. If the charging current is still greater than ten amps, continue to run engine until this figure is reached. Then compare the voltmeter reading with the appropriate setting limits, as specified for the particular control unit as follows.
(Part no. marked on upper edge of the moulded cover of Control Unit).
If reading obtained is stable but outside the appropriate limits the unit can be adjusted as follows.
ADJUSTMENT OF VOLTAGE SETTING
Stop the engine and remove the control unit from its mounting. At the back of the unit is a sealed potentiometer adjuster. Carefully scrape away the sealing compound. Then start the engine, and while running the alternator at charging speed, turn the adjuster slot - CLOCKWISE to INCREASE the setting or ANTI-CLOCKWISE to DECREASE it - until the required setting is obtained.
Recheck the setting by stopping the engine, then start again and slowly "run-up" to charging speed. If setting is now correct, remount the control unit, disconnect test meters and restore original wiring connections. If, after adjustment, the voltmeter reading remains unchanged, or increases in an uncontrolled manner, then the control unit is faulty and a replacement must be fitted.
Test 4
Check of Alternator Output
Disconnect battery earth cable, and connect test ammeter between the alternator main terminal and disconnected cables. Reconnect battery earth cable, and switch on the vehicles full electrical load and leave on for 3 or 4 minutes. Leave load on and start engine and run at approximately 2000 rev/min. The alternator output should balance the load, and at the same time show a charge to the battery.
Check Warning Light Control
If warning light does not function either by remaining "on" or "off", but the system is charging satisfactorily, connect voltmeter between the alternator "AL" terminal and earth. Reading should be 7.0-7.5 max (12 volt alternator) or 14.0-15.0 (24 volt alternator). Connect leads 'E' and 'WL' together. If warning lamp lights the warning light control is faulty and should be replaced.
Fault Diagosis Procedure for 11 AC
Alternator Fails to Charge
a) Check driving belt for correct tension and wear.
b) Apply Tests 1 and 2.
Low-Unsteady Charging Rate
a) Check driving belt for correct tension and wear.
b) Check for high resistance at battery terminals and in the circuit wiring and connection. Check all connections made to earth.
c) Apply Test 2.
Flat Battery or Low State of Charge
a) CHECK condition of battery with hydrometer and high rate discharge tester.
b) Check driving belt for correct tension and wear.
c) Check that the field isolating relay contacts open when master switch is off, otherwise battery will discharge through rotor winding.
d) Check that flat or low battery is not caused by insufficient alternator output caused by abnormal electrical loads by applying Test 4.
Excessive Charge Rate to a Fully Charged Battery
a) Apply Test 3.
Noisy Alternator
a) Alternator loose in mounting brackets.
b) Worn frayed or loose drive belt.
c) Worn bearings, fully out of alignment.
d) Rotor damaged or pulley fan loose on shaft.
e) Open circuited, or short circuited rectified diodes, or stator winding open-circuit.
f) Loose pulley.
Testing the 15ACR, 17ACR, 18ACR, 23ACR, A115/45, A133/55 and LR series in Position
First check the driving belt for condition and tension.
The nominal hot outputs at 6,000 rev/min (alternator speed) are given on Page B.15. These figures may be exceeded slightly when the alternator is running cold. To avoid misleading results, the following test procedure should therefore be carried out with the alternator running as near as possible to its normal operating temperature.
NOTE: De-rated 17 ACR alternators may be fitted to combine harvesters and similar applications where the engine is operating in dusty conditions.
S1
Fig. S.1. illustrates a Test Circuit for 15ACR and 17ACR alternators with standard terminations, battery-sensed.
S2
Fig. S.2. illustrates a Test Circuit for 15ACR and 17ACR alternators with standard terminals and two piece connection plug (machine-sensed).
S3
Fig. S.3 illustrates a Test Circuit for 15ACR, 17ACR, 18ACR, 23ACR, A115/45, A133/55 and LR series alternators with European terminations and single 3 terminal connector plug (machine-sensed). Broken line cable connection applies to battery-sensed, in which case, the connections between the two '+' terminals will not apply and the broken line terminal will be marked "S" instead of '+'.
Value of components in Figs. S.1, S.2 and S.3 are as follows:-
- 1. 12 volt 2.2 watt bulb.
- 2. 0 - 60 ammeter
- 3. 12 volt battery
- 4. 0 - 20 moving coil voltmeter.
- 5. 0 - 15 ohm 50 amp variable resistor.
- 2. 0 - 60 ammeter
Alternator Output Test with Regulator Inoperative
Withdraw the cable connector(s) from the alternator remove the moulded cover (secured by two screws) and earth the regulator green lead or connector strip to frame.
Connect an external test circuit to the alternator output terminals as shown in Figs. S.1, S.2 or S.3.
Observe carefully the polarity of battery and alternator terminals - reversed connections will damage the alternator diodes.
The variable resistor across the battery terminals must not be left connected for longer than is necessary to carry out the following test.
Start the engine. At 1,500 rev/min (alternator speed), the test circuit bulb should be extinguished. Increase engine speed until the alternator is running at 6,000 rev/min approximately, and adjust the variable resistance until the voltmeter reads 13.6 volts. The ammeter reading should then be approximately equal to the rated output (see previous heading). Any appreciable deviation from this figure will necessitate the alternator being removed from the engine for further examination. Failure of one or more of the diodes will be indicated in the above test by effect on alternator output, and also in some instances by abnormally high alternator temperature and noise level.
Regulator Test
The following test assumes the alternator to have been tested and found satisfactory.
Disconnect the variable resistor and remove the earth connection from the regulator green lead or connector strip to frame.
With the remainder of the test circuit connected as for the alternator output test, start the engine and again run the alternator up to 6,000 rev/min until the ammeter shows an output current of less than 10 amperes. The voltmeter should then give a reading of 13.6 - 14.4 volts. Any appreciable deviation from this (regulating) voltage means that the regulator is not functioning properly and must be replaced.
S4
If the foregoing tests show the alternator and regulator to be satisfactorily performing, disconnect the test circuit and reconnect the alternator terminal connector. Now connect a low range voltmeter between the positive terminal of the alternator (the moulded terminal connector is open ended to facilitate this) and the positive terminal of the battery. Switch on battery load (headlights etc.), start the engine and increase speed until the alternator runs at approximately 6,000 rev/min. Note the voltmeter reading.
Transfer the voltmeter connections to the negative terminals of the alternator and battery and again note the meter reading.
If the reading exceeds 0.5 volt on the positive side or 0.25 volt on the negative side, there is a high resistance in the charging circuit which must be traced and remedied.
Dynamo - Models C40A and C40L
General
The following information concerns the two types of dynamo fitted as standard equipment to the 4.236 engine, namely, the Lucas C40A and C40L models. If information concerning another type of dynamo is required, the relevant manufacturer should be contacted.
The C40A is a non-ventilated unit. It will be found fitted to applications such as agricultural machines, which operate under exposed service conditions. The C40L is a ventilated dynamo and will be found on applications such as road vehicles, which operate under cleaner conditions.
Both types are shunt-wound two-pole two-brush machines arranged to work in conjunction with a compensated voltage control regulator unit. A ball bearing supports the armature at the driving end and a porous bronze bush at the rear supports the commutator end. The output of the dynamo is controlled by the regulator unit and is dependant on the state of charge of the battery and the loading of the electrical equipment in use. When the battery is in a low state of charge, the dynamo gives a high output, whereas if the battery is fully charged, the dynamo gives only sufficient output to keep the battery in good condition without any possibility of overcharging. An increase in output is given to balance the current taken by lamps and other accessories when in use.
When fitting a new control box, it is important to use only an authorised replacement. An incorrect replacement can result in damage to the dynamo.
Routine Maintenance
Lubrication
S5
Every 5,000 miles (7,500 km) or 250 running hours, inject a few drops of high quality S.A.E. 30 engine oil into the hole marked "Oil" at the commutator end bearing housing (see Fig. S.5).
Inspection of Brushgear
Every 60,000 miles (90,000 km) or 2,500 running hours, the dynamo should be removed from the engine and the brushgear inspected by an auto-electrician.
Belt Adjustment
Occasionally inspect the dynamo driving belt, and if necessary, adjust to take up any slackness of turning the dynamo on its mounting. Care should be taken to avoid overtightening the belt (Page M.1).
Servicing
Testing in Position to Locate Fault in Charging Circuit
1. Inspect the driving belt and adjust if necessary.
2. Check the connections on the commutator end bracket. The larger connector carries the main dynamo output, the smaller connector the field current.
3. Switch off all lights and accessories, take off the cables from the terminals of the dynamo and connect the two terminals with a short length of wire.
4. Start the engine and set to run at normal idling speed.
5. Clip the negative lead of a moving coil type volt-meter calibrated 0-20 volts, to one dynamo terminal and the positive lead to a good earthing point on the yoke.
6. Gradually increase the engine speed, when the voltmeter reading should rise rapidly and without fluctuation. Do not allow the volt meter reading to reach 20 volts, and do not race the engine in an attempt to increase the voltage. It is sufficient to run the dynamo up to a speed of 1,000 rev/min. If the voltage does not rise rapidly and without fluctuation the unit must be dismantled for internal examination. Excessiv sparking at the commutator in the above test indicates a defective armature which should be replaced.
Starter Motor - Models 2M113, M45G, S12-84 and S12-85
General
This starter motor is a four-pole, four-brush earth return machine with series-parallel connected field coils.
A solenoid-operated pre-engaged drive assembly is carried on an extension of the armature shaft. The main features of this type of drive are as follows:-
a) Positive pinion engagement preventing the pinion being thrown out of mesh whilst starting.
b) Dual-purpose plate-clutch incorporated in the drive assembly giving over-speed and over-load protection.
c) Self-indexing pinion to ensure smooth engagement between the pinion and the flywheel teeth before the starter motor begins to rotate.
d) Armature braking system to ensure rapid return to rest when the starter button is released.
Operation
On turning the starter switch, a solenoid unit mounted on the starting motor yoke is energised and actuates a forked lever to engage the arive pinion with the engine flywheel. On occasions of tooth-to-tooth abutment, axial movement of the pinion is arrested whilst a helically splined sleeve in which the pinion is carried, continues to move forward. This causes the pinion to rotate relative to the flywheel. When the teeth become aligned, spring pressure slides the pinion into mesh with the flywheel.
When the pinion is properly engaged with the flywheel teeth a pair of contacts are closed in the rear of the unit. Closure of the contacts connects the motor to the battery, the armature rotates and the starter pinion commences to crank the engine.
When the engine fires and the starter switch is released, the solenoid unit is de-energised and the spring-loaded plunger withdraws the starter pinion to its out-of-mesh position. The armature is brought rapidly to rest by the centrifugal action of a pair of spring-loaded brake shoes bearing against a brake drum inside the intermediate bracket.
Provision is made to ensure that in the case of the pinion jamming in mesh (this may occur with an engine which falls to start) there is sufficient slack in the engagement lever-to-solenoid plunger linkage to permit the solenoid switch contacts to open.
In the event of the drive remaining in mesh with the flywheel after the engine has run up to speed the starter motor armature is protected from overspeeding by the plate clutch assembly. This clutch allows torque to be transmitted from the starter motor to the engine but not in the reverse direction which is free running.
The clutch is set to slip at between two and three times normal starting torque, thus providing overload protection for the starter motor. Back-firing is a typical example of overloading.
Routine Maintenance
The starter motor requires no routine maintenance beyond the occasional inspection of the electrical connection which must be clean and tight, the brush gear, and the commutator.
After the starter motor has been in service for some time, remove the starter motor from the engine and submit it to a thorough bench inspection.
1. Brush wear (this is a fair indication of the amount of work done). Renew brushes worn to, or approaching, 5/16 in (7,9 mm) in length.
2. Brush spring tension. Correct tension is 30 - 40 oz (0,85 - 1,13 kg). Renew springs if tension has dropped below 25 oz (0,71 kg).
3. Skim commutator if it is pitted or badly worn.
4. Check bearings for excessive side play of armature shaft.
5. Check pinion movement.
6. Clean and lubricate the indented bearing inside the pinion sleeve using Shell SB2628 grease for temperate and cold climates or Shell Retinex for hot climates.
7. Clean and lubricate the indented bronze bearing in the intermediate bracket. Use Ragosine 'Molypad' Molybdenised non-creep oil for this purpose.
Servicing
Testing in Position
Switch on the lamps. If the vehicle is not equipped with lighting, then connect a 0 - 20 voltmeter across the battery terminals before proceeding. Operate the starter control and watch for the following symptoms:-
1. The lamps dim (or voltmeter reading drops to about 6 volts, and the motor does not crank the engine).
Check battey (must be at least half-charged) and battery lugs, (clean and a good earth connection). Check by hand-cranking that the engine is not abnormally stiff.
S6
- a) Poor lug connections at battery.
- b) Bad earth connection.
- c) Broken starter lead, battery to starter.
- b) Bad earth connection.
- a) Faulty solenoid switch.
- b) Open circuit in starter - check brushes.
2. The lamps do not dim, the voltmeter reading remains steady at about 12 volts, and the motor does not crank the engine.
Connect voltmeter from solenoid terminal 'BAT', and starter yoke, operate starter:-
No volts indicated.
Full volts i.e., 12 - 4 volts indicated.
Starter Motor - Model - CA45
General Description
Designed for flange mounting, the C.A.45 starter motor has a uniform cylindrical shape with no surface protrusion. This is because the solenoid and main switch assemblies are housed within the drive end-shield, around (i.e., co-axially with) the armature shaft.
The essential feature of the co-axial starter is that, the pinion alone moves axially to engage the engine flywheel. There is no longitudinal movement of the whole armature assembly, as in the axial types.
Smooth engagement of the pinion with the engine flywheel is constantly ensured by using two-stage operation of the solenoid and switch mechanisms. Thus the risk of damage to both pinion and flywheel, through faulty meshing, is practically eliminated.
In construction, the starter consists of three main sections, into which it can be easily dismantled.
- 1. The solenoid switch-gear and pinion assembly housed in the drive end-shield.
- 2. The armature, shaft and commutator assembly.
- 3. The yoke, pole-piece and field-coil assembly.
- 2. The armature, shaft and commutator assembly.
Ready access is possible therefore, to those parts most likely to require adjustment, such as the switchgear and commutator assemblies.
The starter is designed for working off a 12 volt supply, with 17 amps solenoid current.
Testing on the Vehicle
Ensure that the battery is in a charged condition.
Switch on the lamps and operate the starter button. If the starter fails to function, but the lights maintain full brilliance, check the switch and battery connections to the starter and all external leads. Sluggish action of the starter can be caused by a poor or faulty connection.
Difficulty in smooth engagement between starter and engine flywheel is probably due to dirt on the starter-shaft helices preventing free pinion movement. The shaft should be thoroughly cleaned with kerosene followed by the application of a small quantity of Caltex Thuben 90 or SAE 90 oil.
Operating the Starter
When starting the engine the following points should be rigidly observed
1. Press the starter button firmly and release it immediately the engine fires.
2. If the engine does not fire at once, let it come to rest before pressing the switch again.
3. Do not run the battery down by keeping the starter switch pressed when the engine refuses to start. Ascertain the cause.
4. On some engines it is often helpful to depress the clutch when starting.
5. Do not operate the starter when the engine is running as serious damage may occur to both starter and flywheel.
Maintenance
Lubrication
The large oil reservoir in the drive end shield need only be replenished during overhaul periods, when a supply of Shelltella T27 or BP Energol SHF 100 oil should be added through the oil plug.
An oil impregnated sintered bronze bush is fitted at the commutator end, and needs no further attention.
Brush Gear and Commutator
Inspect the brushes at intervals of approximately 500 hours. See that they are free in their guides and that the leads are quite free for movement, by easing back the brush springs and pulling gently on the flexible connections. If a brush is inclined to stick, remove it from its holder and clean the sides with a petrol moistened cloth.
Be sure to refit the brushes in their original positions to retain the "bedding". The brushes should be well bedded (i.e. worn to the commutator periphery) but if not, wrap a strip of very fine glass or carborundum paper firmly around the commutator with the abrasive side outwards. With the brushes in position, rotate the armature by hand in the normal working direction of rotation; until the correct brush shape is obtained. If the brushes are worn down so that the springs are no longer providing effective pressure, they should be renewed. Check the brush spring pressure by hooking a spring balance under the spring lip. The correct tension is 30 - 40 oz (0,85 - 1,13 kg).
The minimum worn brush length is 1/2 in (12.7 mm). It is essential that replacement brushes are the same grade as those originally fitted. Genuine Perkins spares should always be used. To remove the brushes, unscrew the four fixing screws, one to each brush. In re-assembling care must be taken to re-connect the field coil and interconnector leads, held by two of the fixing screws. Before inserting brushes in their holders, it is advisable to blow through the holders with compressed air or clean them with a cloth moistened with petrol.
The commutator should be clean, entirely free from oil or dirt. Any trace of such should be removed by pressing a clean dry fluffless cloth against it, while armature is hand rotated.
If the commutator is dirty or discoloured, tilt the brushes and wrap a strip of fine glass or carborundum paper (not emery cloth) round the commutator, with the abrasive side inwards. Rotate the armature by hand until the surface is even. Clean with a petrol moistened cloth.
If repair is necessary to the commutator or switch gear etc., the starter must be dismantled. This should be done only in accordance with the method given.
Starter Motor - Model M50
General Description
The model M50 starter motor is a four pole machine of 5 in (127,0 mm) nominal yoke diameter, and has a 21 slot armature.
The drive is of pre-engaged, solenoid operated, push screw type, incorporating a five roller clutch.
The function of the clutch is to prevent the armature being rotated at high speed in the event of the engaged position being held after the engine has started. The solenoid incorporates a two-stage switching arrangement which ensures that the motor develops its maximum torque only when full pinion-flywheel engagement has been achieved.
Testing on the Vehicle
Ensure that the battery is in a charged condition.
Switch on the lamps and operate the starter button. If the starter fails to function, but the lights maintain full brilliance, check the switch and battery connections to the starter and all external leads. Sluggish action of the starter can be caused by a poor or faulty connection.
Difficulty in smooth engagement between starter and engine flywheel is probably due to dirt on the starter-shaft helices preventing free pinion movement. The shaft should be thoroughly cleaned with cleaning fluid followed by the application of a small quantity of Shell SB2628 grease for temperature or cold climates or Shell Retinex for hot climates.
Maintenance
Brush Gear and Commutator
Inspect the brushes at intervals to ensure that they are free in their guides and that the leads are quite free for movement, by easing back the brush springs and pulling gently on the flexible connections. If a brush is inclined to stick, remove it from its holder and clean the sides with a petrol moistened cloth.
Be sure to refit the brushes in their original positions to retain the "bedding". The brushes should be well bedded (i.e. worn to the commutator periphery) but if not, wrap a strip of very fine glass or carborundum paper firmly around the commutator with the abrasive side outwards. With the brushes in position, rotate the armature by hand in the normal working direction of rotation; until the correct brush shape is obtained. If the brushes are worn down so that the springs are no longer providing effective pressure, they should be renewed. Check the brush spring pressure by hooking a spring balance under the spring lip. The correct tension is 30/40 ozf (0,85/1,13 kgf).
It is essential that replacement brushes are the same grade as those originally fitted. Genuine spares should always be used. To remove the brushes, unscrew the four fixing screws, one to each brush. In re-assembling care must be taken to reconnect the field coil and interconnector leads, held by two of the fixing screws. Before inserting brushes in their holders, it is advisable to blow through the holders with compressed air or clean them with a cloth moistened with petrol.
The commutator should be clean, entirely free from oil or dirt. Any trace of such should be removed by pressing a clean dry fluffless cloth against it, while armature is hand rotated.
If the commutator is dirty or discoloured, tilt the brushes and wrap a strip of fine glass or carborundum paper (not emery cloth) round the commutator, with the abrasive side inwards. Rotate the armature by hand until the surface is even. Clean with a petrol moistened cloth.
If repair is necessary to the commutator or switch gear etc., the starter must be exchanged or repaired by an authorised agent.
Every 60,000 miles, (90,000 km) or 2500 running hours, whichever is the sooner, arrange for the examination and service of the starter motor.