The horns and electrical control gear sit together on the bulkhead and chassis area of the engine bay, comprising the audible warning equipment, the dynamo voltage regulator, the fuse protection, and (on TFs and late North American TDs) the direction indicator relay and flasher unit. The arrangement underwent a significant change at chassis TD/8142 in June 1951, when the integrated control box and fuse arrangement was replaced by a separate regulator and fuse box.
Lucas Windtone Horns
Lucas WT618 Windtone horns in paired high-note and low-note configuration provide the dual-tone audible warning. The horns are mounted on the bulkhead via flexible rubber mountings (two per car) that isolate horn vibration from the body structure and prevent stress fractures developing at the mounting points. Handed brackets, left-hand and right-hand bulkhead brackets, locate each horn correctly. Two fastener sets are catalogued: a smaller 1/4 UNF screw, plain nut, and spring washer set (qty 4 each) for the horn-to-bracket fixing, and a larger 5/16 UNF screw, plain nut, and spring washer set (qty 4 each) for the bracket-to-bulkhead fixing.
The horn body specification was updated during TF production in November 1954, but the Lucas type designation WT618 was retained throughout, replacement horns are catalogued as the late TF type, suitable as direct replacements on earlier cars. The high-note horn is supplied without domed covers as standard.
Air Horn Upgrades
For owners wanting a more commanding sound, two air horn options are catalogued as period-style upgrades: a triple Targa pattern and a double Monza pattern. Both are fitted in place of the original Lucas horns and provide significantly higher sound output. These are popular accessories for owners using their cars in modern traffic where the original Lucas horns can be drowned out by general road noise.
Voltage Regulator (Control Box)
The voltage regulator, also known as the control box, manages the dynamo's output to charge the battery and supply the running electrical load. Two regulator specifications are catalogued.
Early TDs to chassis 8141 used the Lucas RF95/2 control box, a 9-post unit with integral fuses, supplied with its own cover. From chassis TD/8142 in June 1951, the Lucas RB106/1 control box (a simpler 5-post regulator without integral fuses) replaced the RF95/2, used in conjunction with the new separate fuse box. The 5-post regulator was carried forward to all TF cars. Each regulator has its own specific cover.
Fuse Box and Fuses
The Lucas SF6 fuse box was introduced from chassis TD/8142 alongside the RB106/1 regulator, replacing the integrated fuse provision in the earlier RF95/2 control box. The SF6 is a two-fuse type with screw terminals, protecting the principal electrical circuits from overload. Two fuse ratings are used, 35 amp and 50 amp glass cartridge fuses, both available individually. Spare fuses should always be carried in the tool kit, as a blown fuse on the road will leave the car immobilised until a spare is available.
Indicator Relay and Flasher Unit
Cars with direction indicators (North American specification TDs from chassis 22315 and all TFs) require an indicator and brake light relay, plus a flasher unit. The relay is a four-screw-terminal unit that handles the higher current of the indicator and brake light circuits. The flasher unit itself is catalogued in two terminal configurations: the original screw-terminal type (the period-correct specification) and an alternative spade-terminal type for cars with later wiring practices. The flasher unit produces the characteristic clicking sound and the indicator pulse rate.
Ordering Considerations
The horn specification is common across TD and TF, the late TF body type is the catalogued replacement for both. Bulkhead brackets are handed; confirm RH and LH when ordering as a pair. The voltage regulator specification is determined by chassis number, RF95/2 (with integral fuses) for TDs to chassis 8141, RB106/1 (with separate fuse box) for TDs from chassis 8142 and all TFs. The fuse box itself is the same SF6 type for all cars from TD/8142 onwards.
Air horn upgrades are common to both TD and TF. The flasher unit terminal type (screw or spade) is a customer choice. The indicator relay is required on cars with factory or retrofitted direction indicators.