Turn Signal Bulb - Rear

Replace the rear turn signal bulb on a 1972 Ford F-100 by accessing the taillight assembly from the rear of the vehicle.

Warnings

Tools required

Parts

• Rear turn signal bulb × 1 — 1157 dual-filament bulb

Preparation

1. Park vehicle on level surface and turn off ignition
2. Ensure turn signals and all lights are off
3. Open tailgate for easier access to rear taillight assemblies

Procedure

1. 1

   Locate the taillight assembly
   Identify which rear taillight assembly contains the failed turn signal bulb. On the 1972 F-100, the taillight assemblies are mounted on each side of the rear of the bed, on either side of the tailgate (Styleside) or on the rear fenders (Flareside/Stepside). On the 1972 F-100, the turn signal typically shares the red lens with the tail/brake light using a dual-filament bulb; there is generally no separate amber turn signal lens.
2. 2

   Access the bulb socket from inside the bed
   Access to the bulb may be from behind the assembly or, more commonly on this truck, by removing the lens retaining screws from the outside of the taillight assembly to expose the bulb. Verify your specific taillight design before proceeding.
3. 3

   Identify the turn signal socket
   The turn signal socket corresponds to the amber or upper portion of the lens. The stock 1972 F-100 taillight typically uses a single dual-filament 1157 bulb that serves the tail, brake, and turn signal functions; a separate reverse lamp may or may not be present depending on trim. Identify the socket(s) present in your assembly. Identify which socket feeds the turn signal based on lens position.
4. 4

   Remove the bulb socket
   Grasp the socket housing firmly and rotate counterclockwise approximately 1/4 turn. Pull the socket straight out from the taillight housing. The socket should release with moderate pressure.
5. 5

   Remove the failed bulb
   The 1157 bulb has offset pins and a bayonet base. Press the bulb gently into the socket while rotating counterclockwise approximately 1/4 turn until the pins align with the wider portions of the socket slots. Pull the bulb straight out of the socket.
6. 6

   Inspect the socket
   Examine the socket contacts for corrosion, burning, or damage. If corrosion is present, clean contacts with a small wire brush or fine sandpaper. Check that the socket body is not cracked or melted. Replace socket if damaged.
7. 7

   Install the new bulb
   Insert the new 1157 bulb into the socket with the offset pins aligned to the wider portions of the slots. Press in gently and rotate clockwise approximately 1/4 turn until the bulb locks into place. The bulb should be secure and not rotate freely.
8. 8

   Reinstall the socket assembly
   Insert the socket back into the taillight housing, aligning the tabs on the socket with the slots in the housing. Push in firmly and rotate clockwise approximately 1/4 turn to lock the socket in place.

Reassembly

1. Ensure socket is fully seated and locked into taillight housing
2. Close tailgate if opened during procedure

Verification

• Turn ignition to accessory or on position
• Activate turn signal in the direction of the replaced bulb and verify it illuminates properly with regular flashing
• Check that the turn signal indicator on the dash flashes at normal rate (not rapid, which would indicate a bulb still out)
• Test hazard lights to confirm bulb operates in hazard mode
• Visually inspect that no light leaks around the socket area when illuminated

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