This section covers products that improve lighting performance, charging reliability, and audible warning beyond original specification. Sixty-plus years on, the original 12-volt positive earth Lucas system meets a different operating environment, more night driving, faster traffic, longer storage, and additional accessory loads, and the upgrades catalogued address these practical limitations without altering the period character.
Battery Chargers & Horns
A battery left to self-discharge during storage is the single most common cause of starting failure on a TD or TF returning to use after a winter layup, as the lead plates sulphate progressively as the battery sits below full charge and the damage is cumulative. An automatic conditioner connected permanently to the battery terminals monitors the charge state and applies a maintenance current only when needed, while conventional chargers in 6-and-12-volt and 12-volt-only specifications are also catalogued for owners who prefer to charge manually before extended runs. The TD and TF were originally fitted with a paired low-note and high-note horn arrangement on the bulkhead, and replacement horns based on the late TF pattern are catalogued for owners renewing tired units, also suitable for fitment to earlier cars, while for owners wanting a more commanding sound, Targa triple and Monza double air horn sets are available, both delivering significantly higher output than the original electromagnetic horns.
Lighting Upgrades
Lighting is the most extensive area, reflecting the practical importance of better lighting on a car designed when speeds were lower and roads less crowded. 7-inch halogen headlamps are direct replacements giving significantly improved beam over sealed-beam or pre-focus tungsten, with optional H4 bulbs, while LED replacements for sidelamps, indicators, rear lamps, and instrument illumination provide better brightness with dramatically reduced current draw, and fog and driving lights are available in period or modern patterns, alongside bulbs across tungsten, halogen, and LED specifications. When fitting halogen bulbs at higher wattages, typically 100/80 watt rather than the standard 60/55 watt, the additional current draw exceeds the comfortable rating of the original light switch contacts and the wiring harness, so a headlamp relay kit takes the high-current load off the switch and harness by using the original switch only as a low-current trigger for the relay, which then handles the headlamp current via heavier-gauge cable, strongly recommended whenever a wattage uprating is undertaken.
Polarity & Ordering
The TD and TF were both supplied as positive earth from the factory, but many cars have been converted to negative earth at some point, so every electrical upgrade must be specified for the correct polarity. LED bulbs in particular are polarity-sensitive, as a positive earth LED will not illuminate on a negative earth car and vice versa even though the same bulb-fitting body is used, and battery chargers and conditioners must also be matched to the car's polarity and rating, so when ordering any electrical accessory the car's current polarity should be confirmed rather than relying on factory specification alone. The 7-inch headlamp size is universal across TD and TF, and for air horn upgrades the mounting space behind the grille is the practical limit, the Targa triple sets needing more space than Monza doubles, with TD owners likely to find space tighter than TF owners.