1. Fuses: This is the first thing to check. Your owner's manual will show you the fuse box location(s) and the fuses responsible for the brake lights and turn signals. Check these fuses carefully, even if they *look* okay; a blown fuse can sometimes have an internal break that's hard to see. Replace any blown fuses with the correct amperage.
2. Bulbs: Burnt-out brake lights and/or turn signal bulbs are common. Check all the bulbs (including the ones in the rear, and any on the sides) to ensure they're working.
3. Multi-Function Switch (Turn Signal Switch): Located on the steering column, this switch controls the turn signals, hazard lights, and often the cruise control. A faulty multi-function switch is a frequent culprit for non-functioning turn signals and brake lights. It's relatively inexpensive to replace but can be tricky to access and install.
4. Brake Light Switch: Located near the brake pedal, this switch activates the brake lights when the pedal is pressed. A faulty brake light switch will prevent the brake lights from working, but the turn signals might still work. It's a relatively easy part to replace.
5. Wiring: Damaged, corroded, or loose wiring in the circuits leading to the lights can cause intermittent or complete failure. This is a more difficult issue to diagnose and requires careful inspection of the wiring harness, especially around the taillight assemblies and connectors. Look for broken wires, corrosion, or loose connections.
6. Grounding Issues: Poor grounding can prevent the electrical signals from completing the circuit. Check the ground connections at the taillights and the chassis for corrosion or loose connections.
7. Turn Signal Relay: This relay controls the flashing of the turn signals. A faulty relay can cause the turn signals to not work at all or to flash erratically.
8. Hazard Light Switch: If the hazard lights also don't work, it could point to a problem with the hazard light switch itself, or a more general electrical issue.
9. BCM (Body Control Module): In some cases, a faulty Body Control Module can affect the operation of lighting systems. This is less likely but possible, and diagnosis would require more advanced tools.
Troubleshooting Steps:
1. Start with the simplest: Check the fuses and bulbs first.
2. Test the brake light switch: With the key on, press the brake pedal and test the voltage at the brake light wires using a multimeter. If there's no voltage, the switch is likely bad.
3. Visually inspect wiring: Look for any obvious damage or corrosion in the wiring harness.
4. Check grounds: Ensure good ground connections at the taillights and chassis.
5. If the problem persists: Consult a wiring diagram specific to your 1996 Ford E-250 to trace the circuits systematically. A professional mechanic may be necessary for advanced diagnosis and repair.
Remember to always disconnect the battery's negative terminal before working on any electrical components to avoid injury.
