1. Verify Bulb Socket Contacts:
* Thorough Inspection: Even with new bulbs, ensure the bulb sockets are clean and making good contact with the bulb terminals. Corrosion or a bent contact can prevent the bulb from lighting. Use a multimeter to check continuity between the socket and the bulb terminals.
* Socket Ground: A bad ground connection at the socket is a common culprit. Check the metal contact points on the socket for corrosion and make sure the socket is securely grounded to the car body.
2. Check the Wiring Harness:
* Visual Inspection: Carefully inspect the wiring harness leading to the tail lights. Look for any broken wires, frayed insulation, or areas where the wires might be pinched or chafed. Pay close attention to the area where the harness enters and exits the body.
* Continuity Test: With the multimeter, check the continuity of the wires from the tail light sockets to the fuse box (and then to the switch). You'll need a wiring diagram for your specific car model to identify which wires are for tail and brake lights.
3. Test the Brake Light Switch:
* Location: This switch is usually located on the brake pedal assembly.
* Testing: With the multimeter, check if the switch closes (shows continuity) when the brake pedal is pressed. You might need a helper to press the brake while you test. A faulty switch is a very common cause.
4. Investigate the Tail Light Switch (if separate):
* Some vehicles have a separate switch for the tail lights. Consult your wiring diagram to locate it. Testing is similar to the brake light switch.
5. Check the Multi-Function Switch (Turn Signal Switch):
* This switch controls various functions, including turn signals, hazards, and sometimes the tail lights. If this is faulty, it can impact tail and brake lights. It is more difficult to test and you might need to replace the entire switch as repair is generally not cost effective.
6. Wiring Diagram:
* Essential: You absolutely need a wiring diagram specific to your 1988 Chevrolet Celebrity. This will show you which wires connect to what components, allowing you to pinpoint the problem area effectively. You can often find these online through auto parts websites or repair manuals.
7. Ground Connections:
* Body Ground: Poor grounding can affect multiple electrical circuits. Check all ground connections near the tail lights and battery for corrosion or looseness.
8. Relay (If Applicable):
* Some systems use relays. If your wiring diagram shows a relay for the tail lights, test it for proper operation.
9. Consider a Professional:
If you are not comfortable working with car electrical systems, take your car to a qualified mechanic. Improper electrical work can lead to further damage.
Remember to disconnect the negative battery terminal before starting any electrical work. Safety first! Good luck!
