Lucas C40 type Dynamo for Classic vehicle applications

The C40 generator is a shunt-wound two pole two brush machine designed to work in conjunction with a compensated voltage control regulator unit. Output is controlled by the regulator control box and is dependent on the vehicle battery state of charge and the electrical loading during vehicle operation.
When the battery is in a low state of charge the generator gives a proportionately higher output to keep the battery in good order and supply additional electrical loads such as lighting.

2023 Replacement C40 & C40-1 type Dynamo prices from £80 plus carriage part no.HC110483 replacing Lucas LRD101

4 1/2 inch fan diameter : 20A

5 inch fan diameter: 22 Amp

Field coil resistance : 6 ohms

HC110483

Lucas Part Nos: NDB100 , LRD100, Lrd00107, 22250, 22258, 22272, 22295, 22297, 22700, 22700N, 22700L, 22700R, 22704, 22704A, 22704d, 22704h, 22704j, 22704i, 22705, 22705f,22705l, 22715, 22715e, 22715f,22715,h, 22715j, 22715k, 22717, 22725, 22742, 22742e, 22742k, 22747, 22747a, 22747b, 22748, 22748a, 22748b, 22754, 227542, 22765, 22765b, 22765j, 22767, 22767d, 22767f, 22775, 22775a, 22775e, 22785, 22785a, 22785d, 22789, 22789a, 22789d, 26021103,

B90 exchange unit

Austin Rover part no : AEJ12

Perkins part nos : 2871153, 2871161 , 2871178, 34263,

Ford part nos : 69EB10002C1, 69EB10002CA

Massey Ferguson part no: 3112299R91

Aftermarket: HC110482 (22Amp) , HC110483 (11Amp), WG5

C40 Dynamo Rebuild Parts Bill of Materials

Lucas C40 Dynamo Checks and Tests

Check condition and tension of dynamo drive belt.

Ignition warning lamp (WL) should illuminate with ignition key on and extinguish when the engine is running. Check the dynamo and control box is wired correctly.

Residual field : Disconnect cables from dynamo , connect voltmeter between D terminal and chassis ground. Engine at approx 1500 rpm , Volt meter reading should be 1 to 3 volts

C40 Dynamo field circuit : Voltmeter connected between D terminal and chassis ground. Ammeter connected between D terminal and F terminal. Increase engine rpm until voltmeter reads nominal system voltage. Ammeter should read aprox 2 amps.

C40 Dynamo armature circuit : Disconnect cables , connect volt meter Black lead to D terminal , Red lead to Earth, run engine 1500rpm , meter reading should be 2 to 4 volts.

On dynamos with open ventilation the commutator condition may be partly seen without major disassembly. The commutator should be clean and free of grease with a polished appearance, free from pitting . The brush gear should be examined for wear ensuring carbon brushes travel freely within the brush holders and contact the commutator under brush spring tension. Brushes below 1/4 inch length (6mm) should be renewed. The armature may be checked for condition after disassembly of the dynamo by use of an armature growler, or otherwise by substitution. Field coil resistance may be checked using an ohmeter between the field terminal and the yoke (casing). Resistance of approx 6 Ohms is expected. Alternatively field coil continuity can be checked using a 12v DC supply and ammeter which should read approx 2 Amps. No reading on the Ammeter indicates field coils to be open circuit and requiring renewal. To replace field coils a pole shoe expander an wheel operated screwdriver may be required. Armature shaft bearing bushes should be replaced if they allow excessive side movement of the armature shaft. Before bushes are refitted they should be immersed in a thin engine oil for 24 hours. A shouldered mandrel will be required to press in new bushes/bearing to commutator end and drive end brackets.

Regulator Setting Data

Information sourced from Rootes group workshop manual for Hillman :

The regulator is set during manufacture and generally should not need adjustment unless the battery does not stay charged or overcharges.
Specific manufacturers settings should be followed.
Open circuit regulator settings are dependent on temperature and should be completed ithin 30 seconds otherwise flse readings may result.
A dynamo run at high speed on open circuit will build up high voltage. Do not run engine above half throttle or false setting will be made.
It is important to check that a low battery SOC is not due to a slipping drive belt, defective dynamo, or defective battery or wiring connections before making adjustment

Flashing the C40 Dynamo

Flashing the dynamo is required to polarise dynamo output to suit either Negative earth or Positive Earth vehicles.
With the dynamo mounted on the vehicle, remove D & F leads, touch a wire between the dynamo F terminal and battery live terminal.

C40 Dynamo to Alternator Conversion

A range of aftermarket products are available offering bolt on replacement units with similar appearance to the original C40 dynamo but offer higher current output as alternator conversions.
Alternator benefits include higher output at lower engine revolutions.
Increasing generator charge current output may require upgrading cable specification between generator and vehicle battery.

C40 dynamo Car & Light Commercial applications

Legal disclaimer : Any information on this web page is given in good faith but should not be relied upon as correct. all brands and trade names are respected as property of their legal owner with no association express or implied. By use of this website you accept and understand our terms and conditions which can be read by following the link: Terms