Energise electrics

It’s dark and cold out there. If you are heroically driving your (rustproofed) classic car through these damp, gloomy evenings, you will be acutely aware of the need for ample amps and volts to keep headlights, wipers and heater blower working even while sitting in a jam with the engine idling.

Your classic, if made before the early 1970s, could well have a dynamo to supply its electrical needs. When your car is idling in those jams, with the above items all switched on, the dynamo won’t be producing as much power as they consume and your battery will gradually go flat. The ammeter, if the car has one, will be showing a discharge and the red ignition light may be glowing.

Of course, you would have no such trouble in the summer. Or would you? Perhaps you have replaced the original engine-driven cooling fan with an electric one, which takes a lot of power. Again, in traffic the dynamo might not be able to keep up with demand. What you need is an alternator: strong power even at idling speeds, and more power overall.

How to go about this depends on the car and your desire to keep an original look under the bonnet. A modern alternator might be easy to fit if you can find a suitable drive pulley and can position it in line with the other pulleys, but it may look out of place. Later versions of your car may have had an alternator when new, so finding one plus the required bracketry should be easy and it will still look right.

Or you could buy one of the popular alternators that look like an original dynamo but have modern parts inside, such as a Powerlite or a Dynamator. Specialist firms can build an alternator into your original dynamo’s casing, too, if you prefer.

It’s easy to wire up provided the alternator has its own internal regulator (only some very old ones don’t). You just need a fairly thick wire from the battery’s live terminal – the power feed to the starter solenoid is a convenient connection point – to the alternator’s output terminal, and to connect the alternator’s smaller terminal to the ignition warning light. You can get rid of the old regulator control box, unless you want to retain it for the look. Some existing wiring can usually be repurposed, at least for the warning light.