* Faulty power lock switch: The switch itself might be broken or worn out.
* Wiring problems: A break or short in the wiring harness leading to the locks is common in older cars. This could be anywhere from the switch to the lock actuators.
* Faulty lock actuators: The motors in the car doors that actually move the locks may have failed.
* Bad relay: The power locks might use a relay to switch the power. A failed relay would prevent the locks from working.
* Low battery voltage: A weak battery might not provide enough power to operate the locks reliably.
How to troubleshoot:
1. Check the fuses: This is the easiest first step. Consult your owner's manual to locate the fuse(s) for the power locks and check them with a test light or multimeter. Replace any blown fuses. If replacing the fuse blows it immediately, you have a short circuit somewhere in the system.
2. Test the power lock switch: Use a multimeter to check if power is getting to the switch when activated.
3. Check the wiring: This is more involved and requires some electrical knowledge and tools. You might need to trace the wires from the switch to the actuators.
4. Test the lock actuators: You can often hear a clicking sound from a functioning actuator when the switch is pressed. A lack of clicking suggests a failed actuator. If you have a multimeter you can check the voltage at the actuator itself.
5. Battery voltage: Use a multimeter to measure the voltage of the battery. A low voltage could prevent proper operation.
If you're not comfortable working with car electrical systems, it's best to take your Cadillac to a qualified mechanic for diagnosis and repair. Attempting to fix electrical issues without the proper knowledge and tools can lead to further damage.
