Bulbs, Interior - Exterior

Bulbs, Interior – Exterior

This category supports the Electrical lighting circuits for 1932-1972 Passenger car, 1939-1970 Mercury, 1932-1979 PU applications. Every lighting function—headlights, tail lights, interior dome lights, dash indicators, fog lights, and spot lights—depends on correct voltage, correct bulb type, and proper socket contact. A mismatch in any of those areas creates dim output, overheating, or repeated failure.

In restoration work, bulb issues are often misdiagnosed. A vehicle may appear to have weak headlights or intermittent tail lights when the real cause is incorrect voltage selection between 6V and 12V systems, poor grounding, or degraded light sockets. Installing the correct bulb style is only one part of restoring proper illumination.

Exterior lighting carries load through headlight switches, dimmer switches, and dedicated circuits. Interior lighting relies on door jamb switches and dash control rheostats. Each circuit requires the correct filament configuration and base style to operate as designed. Using the wrong bulb can overload wiring or reduce visibility.

Light output is only as reliable as the socket and ground supporting it.

Subsystem Definition – Illumination & Voltage Integrity

The bulb subsystem converts electrical energy into visible light within the broader Electrical architecture. It operates across multiple circuits: headlight high/low beam, tail and brake illumination, interior dome circuits, and auxiliary lighting such as fog and spot lights.

System voltage determines bulb selection. 6V Exterior Bulbs and 6V Interior Bulbs are specific to original 6-volt systems. 12V Exterior Bulbs, 12V Interior Bulbs, and 12V Miscellaneous Bulbs serve converted or factory 12-volt systems. Installing a 6V bulb in a 12V system results in immediate failure. Installing a 12V bulb in a 6V system produces weak output.

Headlight systems may use 6V or 12V Sealed Beam, 6V or 12V  Halogen. Vehicles with stock reflector assemblies require the correct Headlight Bulb For Stock Reflectors. Tail Lights can use -  6V or 12V Halogen,  or stock 6V or 12V Tail Light Bulbs.  Halogen options must match housing design and circuit load.

Auxiliary lighting includes Spot Light & Fog Light assemblies.

Component Breakdown – Functional Integration

• 6V Exterior Bulbs / Bulbs - Exterior, 6V – Exterior illumination for original 6-volt systems.
• 12V Exterior Bulbs / Bulbs - Exterior, 12V – Exterior lighting for 12-volt systems.
• 6V Interior Bulbs – Dome, courtesy, and dash applications in 6-volt vehicles.
• 12V Interior Bulbs / 12V Miscellaneous Bulbs – Interior and specialty circuits in 12-volt systems.
• 12V Led Bulbs – Low-current alternatives for 12-volt applications where compatible.
• Headlight - Sealed Beam, 6V & 12V – Self-contained headlight units.
• Headlight - Halogen, 6V & 12V – Replaceable filament-style headlight options.
• Headlight Bulb For Stock Reflector – Correct bulb geometry for factory reflector housings.
• Tail Light - Halogen, 6V or 12V – Rear illumination matched to system voltage.
• Fog Light/Spot Light Bulbs -  Auxiliary forward lighting components.

Each selection must align with system voltage, socket type, and housing configuration.

Fitment & Variation

Lighting configuration varies by year, body style, and whether the vehicle retains its original voltage system. Some vehicles use sealed beam headlights; others use reflector housings with replaceable bulbs. Tail light housings differ in filament count and grounding method.

LED options require compatible 12-volt systems and proper polarity. Vehicles originally equipped with 6-volt systems must retain matching bulb specifications unless converted.

Fitment will vary by model year or suspension configuration.

Identify the correct voltage and housing style before replacing bulbs.