Lucas C45YV-3, type L1 (12V), clockwise rotation with Earth return. Lucas part numbers 22449A (Briggs) to 22449D (Barker). Lucas service number 228139.
Terminal cover is Lucas part #238234.
Body is stamped with (eg.) 228139 2 49 - where last digits probably represent the month and year (February 1949 in this case - cf. Ignition Coil).
Resistance (measured) (Field to Earth) (approx.) 6Ω
Brush spring tension is 15-25 oz.
If the brush spring is suspected of being weak (see problems below), test with a small spring scale. If the tension is low, fit a new spring.
If new brushes are required, remove the old as described below ('removal') and place the new brush in the holder and gently lower the spring. Secure the eyelet on the end of the brush lead in the original position.
The new brushes must be bedded to the commutator as follows:
1) Pass a thin strip of very fine glass paper between the commutator and each of the brushes so that the abrasive surface is towards the brush faces and turn the armature in its normal direction of rotation for a few minutes and then remove the glass paper
2) Wipe away carbon or sand paper dust after the operation (best removed by blowing the dynamo out with a pump or compressed air with the machine in motion)
3) After several days' running the brush gear should again be examined, and any carbon dust wiped away
If the brush is suspected of sticking (see problems below), test by holding back the brush spring and moving the brush in its holder. If the brush tends to stick, remove it and clean with petrol.
A commutator in good condition will be smooth and free from pits or burned spots, if it is not, clean with a cloth moistened with petrol. If this is ineffective, carefully polish with a strip of fine glass paper. Pass the glass paper round the commutator and draw it backwards and forwards while the armature is slowly rotated.
If the regulator fails to regulate the output correctly, the dynamo may burn out. The field coil will need replacing/rewinding (an open circuit reading when measuring across (F)ield and (D)ynamo is a possible indication of this).
Higher resistance readings across (F) and (D), or open circuit readings, may indicate dirty/damaged brushes or housings.
The heads of the brass screws holding the brushes in place are extremely prone to take damage, making subsequent removal or replacement difficult. Take care to use the correct sized screwdriver.
The use of more commonly available, narrow replacement brushes may lead to 'chatter', causing chipping and rapid wear.
Failure to keep the ball race greased may lead to bearing failure.
If the battery is in a low state of charge it may indicate broken or loose connections, dirty or worn commutator, worn or sticking brushes, weak brush springs, or brushes not bedding. There is also a (more remote) chance that the field coils or armature are damaged.
1) Remove top securing screw and 2 bottom bolts
2) Although awkward on account of the weight, the dynamo can now be maneouvered past the securing bracket and out of the fan belt.
It may be necessary (or easier) to remove the O/S horn and dynamo securing bracket first.
To remove brushes:
1) Remove dynamo cover band
2) Remove screw securing eyelet on end of lead from brush
3) Hold back brush spring and remove brush from its holder.
A modern alternator, built to look like a Lucas C45, is available but requires some modifications to be made, including switching all the electrics to negative earth.
Commercial Ignition produced a dynamo brush set CI.277, noted to replace (Lucas) part 227541 and part 105E.10043, apparently used on Ford, Austin, Vauxhall, Rover and Hillman vehicles. The width is a little less than the original brush, at 5.5mm compared with 7mm, but is otherwise an excellent fit. Take care when using narrow brushes to adapt the housing, or pad the brushes to avoid chatter (see problems above).
For a better fitting replacement brush, an oversized brush can always be filed to size.
The C45 was also used in the MG TA/B/C models. Bushes, bearings and brushes may therefore be available from T-Type parts suppliers.
The ball race is a standard 6203 bearing and may be obtained from many stockists - it is recommended to replace with a sealed unit such as 6203-2Z or 6203-2RS.
If replacing the bronze bush (rear of unit), soak the replacement in oil for 24hrs before pressing it in.
The dynamo should deliver maximum current at approximately 20mph (based on period literature). At this point, the regulator will come into operation.
Lucas dynamo brush kit part #D40 may be suitable for this dynamo.
For a detailed breakdown of components and Lucas part numbers, see this link.