Fog Light Assembly

This procedure covers the installation of aftermarket fog light assemblies on a 1972 Ford F-100, including mounting, wiring, and switch integration.

Warnings

Tools required

Parts

• Fog light assembly kit (pair) × 1 — Aftermarket 5-7 inch round or rectangular fog lights
• Fog light wiring harness with relay × 1 — Universal fog light harness with 30A relay
• Inline fuse holder with 15A fuse × 1 — ATO/ATC blade fuse holder
• Dash-mounted toggle switch × 1 — SPST 12V toggle switch
• Mounting brackets × 1 — Universal L-brackets or vehicle-specific fog light brackets
• Butt connectors (assorted) × 10 — 16-14 gauge butt connectors
• Ring terminals (assorted) × 4 — 16-14 gauge ring terminals
• Heat shrink tubing × 1 — Assorted sizes
• Self-tapping screws or bolts × 8 — 1/4"-20 or similar for mounting

Preparation

1. Park vehicle on level surface and set parking brake.
2. Disconnect negative battery cable and isolate from battery terminal.
3. Determine fog light mounting location on front bumper or frame rails, ensuring lights will be positioned symmetrically and below headlight level.
4. Verify fog light kit contents include both housings, bulbs, lenses, mounting hardware, and wiring harness.
5. Plan wire routing from fog lights through engine bay to firewall and into cabin for switch connection.
6. Identify suitable power source (headlight circuit or direct battery connection with fusing).

Procedure

1. 1

   Determine and mark mounting locations
   Position fog lights on the front bumper or frame horns approximately 18-24 inches apart (center to center). Ensure lights are level and symmetrical. Mark mounting hole locations with center punch or marker. Verify clearance from suspension components, steering linkage, and that mounting location provides adequate protection from road debris while allowing proper forward illumination.
2. 2

   Drill mounting holes
   Using the marked locations, drill pilot holes for mounting hardware. If using existing bumper holes, verify fit with mounting brackets. For new holes in the bumper or frame, drill holes sized appropriately for the mounting hardware provided (typically 1/4 inch for bolts or self-tapping screw size). Deburr all holes and apply touch-up paint or rust inhibitor to prevent corrosion.
3. 3

   Install fog light mounting brackets
   Attach mounting brackets to the drilled locations using the provided bolts, nuts, and washers, or self-tapping screws. Ensure brackets are oriented correctly for fog light attachment and are level. Tighten hardware securely but avoid overtightening thin bumper metal.
4. 4

   Mount fog light assemblies
   Attach fog light housings to the installed brackets using the hardware provided with the fog light kit. Position lights with the adjustment mechanism accessible for later aiming. Leave mounting hardware slightly loose to allow for final adjustment after wiring is complete.
5. 5

   Route fog light wiring to engine bay
   Route the fog light power wires from each light assembly along the frame rail or behind the bumper toward the engine bay. Use zip ties or wire loom to secure wiring away from hot exhaust components, moving suspension parts, and sharp edges. Route wires through an existing grommet in the firewall or create a new protected pass-through to reach the cabin area where the switch will be mounted.
6. 6

   Install relay and fuse near battery
   Mount the fog light relay in the engine bay on the firewall or inner fender using a self-tapping screw or existing bolt location. Install the inline fuse holder in the power supply wire between the battery positive terminal and the relay (terminal 30). Use a fuse rated for the fog light load (commonly 15A for LED/low-wattage pairs, up to the harness maximum for higher-wattage halogen lights); verify against the fog light wattage rating. Connect a ring terminal to the power wire and attach to the positive battery terminal or to a suitable fused power source such as the headlight switch output.
7. 7

   Ground the relay and fog lights
   Connect the relay ground terminal (terminal 85 or as marked on relay) to a clean, bare metal ground point on the firewall or engine block using a ring terminal and existing bolt. Connect the negative/ground wires from both fog lights to the common ground point or to a separate nearby ground location on the frame. Ensure all ground connections are clean, tight, and free of paint or corrosion.
8. 8

   Connect fog light power outputs to relay
   Connect the positive power wires from both fog lights to the relay output terminal (terminal 87). Use butt connectors or solder connections with heat shrink to join the two fog light wires together, then connect to the relay. Ensure all connections are secure and insulated to prevent shorts.
9. 9

   Install dash-mounted control switch
   Select a suitable location on the dashboard for the fog light toggle switch, preferably near other lighting controls. Drill a hole sized for the switch body (typically 1/2 inch for standard toggle switches). Mount the switch through the hole and secure with the provided nut and washer from behind the dash.
10. 10

    Wire switch to relay trigger circuit
    Run a wire from one terminal of the dash switch through the firewall to the relay trigger terminal (terminal 86). Connect the other terminal of the switch to a switched 12V power source (such as the accessory circuit or a headlight circuit wire) to ensure fog lights only operate when ignition is on or headlights are active. Use butt connectors or soldered connections with heat shrink tubing for all connections. This ensures the relay coil is energized only when the switch is closed and power is available.
11. 11

    Reconnect battery and test operation
    Reconnect the negative battery cable. Turn on the vehicle ignition or headlights (depending on wiring configuration). Flip the fog light switch to the on position and verify both fog lights illuminate. If lights do not work, use a multimeter or test light to check for power at the relay, switch, and fog light connectors. Verify all ground connections are secure.
12. 12

    Aim fog lights
    Park vehicle 25 feet from a wall or garage door on level ground. Adjust each fog light using the adjustment screws so the beam pattern is low and wide, illuminating the road surface approximately 15-20 feet in front of the vehicle without creating glare at eye level. Both lights should have symmetrical and even beam patterns. Tighten all fog light mounting hardware once aiming is complete.
13. 13

    Secure all wiring
    Perform a final inspection of all wiring routing. Use additional zip ties or wire loom to secure all wires away from moving parts, heat sources, and sharp edges. Ensure no wires are hanging loose or rubbing against components. Verify all connectors are fully seated and all electrical tape or heat shrink is properly applied.

Reassembly

1. Verify all mounting hardware is tightened securely.
2. Confirm all electrical connections are insulated and protected from moisture.
3. Check that fog light lenses are clean and properly sealed.
4. Ensure all wiring is routed safely and secured with zip ties or loom.

Verification

• Turn ignition or headlights on and activate fog light switch; both fog lights should illuminate immediately.
• Verify fog lights turn off when switch is toggled off.
• Check that fog light beam pattern is aimed low and wide without causing glare.
• Inspect all mounting points to ensure fog lights are secure and do not vibrate excessively.
• Confirm no electrical shorts or blown fuses after installation.
• Road test vehicle to verify fog lights remain secure and functional during operation.

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