Technical - Electrics

General Specifications

Dynamo 1946-1948 Lucas MC45 \ 1949-1956 Lucas MC45L
Battery 6V 12AH
Ignition Coil CQO L11
Spark Plug Champion NA8 or N8B
Distributor AC 564
Headlamp 8 Inch Diameter - 056452-B
Headlamp Bulb 6V 24/24 Watts
Pilot Bulb 6V 3 Watts
Tail Bulb 6V 3 Watts
Stop and Tail (Where Fitted) 6V 3/18 Watts
Oil and Ignition Warning Lamps 2.5V 0.2 Amp MES Fitting
Charging System CVC (Compensated Voltage Control)
Contact Breaker Gap .012" - .015"
Stewart Engineering Replacement Distributor WCB172

Rebuilding Altette Horns - Sourced from

Amateur's Guide to Horn Restoration: I've stripped and repaired several horns and there's not much to them. They contains a coil, and set of points and a diaphragm. The points are in series with the coil and when they open, the coil's magnetic field collapses. They are so positioned that when current enters the horn  the coil pulls the diaphragm inwards and opens the points which collapses the field which releases the diaphragm  which closes the points and gives us magnetism again and again and again... .

My steps are:
1. Disassemble - You shouldn't have to open the big nut in the middle of the Diaphragm but open everything else.
2. Clean any spider nests and rust out of the inside.
3. Check the current path for opens or shorts.
4. Clean the points and all screwed connectors to bare metal.
5. Clean and oil all threads.
6. Check coil for continuity. If it is bad, give up and get it rewound or find another horn.   If you don't have a meter, briefly apply voltage through the coil and see if you get magnetism.
7. Make sure the adjusting screw on the back really does change the point gap when turned and the spring works.
8. Reassemble and test. Use adjuster on the back to adjust the horn tone and volume. If it makes just one pop of the diaphragm when you try it, the points are not opening when the diaphragm pulls in. If it makes no noise, then the points are open when current is initially applied and they should start out closed.
9. When you get some noise, turn the adjusting screw till the sound stops in both directions and pick the best tone in between.
Be especially careful where wires attach to the back. If they are open and can get wet, it can short from the connection to the horn body and cook all your wiring. On the Vincent the horn wire is always hot and it's activated  by providing a ground path with the switch. An inline fuse is advisable.
10. Polish, paint, re-chrome or whatever you like to the outside and you're in business.

Also See: SUNBEAM: Modifications.

The Dynamo

Also see: SUNBEAM: Modifications.


S7 Wiring Diagram