If you find that the brake lights on your Volkswagen Passat are not illuminating, you can follow these steps for inspection and resolution:
First, check the brake light switch. If the switch is faulty, all brake lights will fail to illuminate. During maintenance, try to connect the brake light switch directly with a wire. If the brake lights turn on, it indicates the switch is damaged and needs to be replaced.
Next, inspect the brake light bulb. Frequent usage can wear out the bulb or break its filament, causing it to not light. Check if the bulb is intact, and replace it if it is damaged.
Then, check the fuses. If both the bulb and switch are functioning properly, inspect the fuses. Some vehicles share a single fuse for the brake lights and other electrical components, so check the operation of other electrical devices and replace the corresponding fuse if any are malfunctioning.
After that, check the connectors in the brake light wiring harness. Locate the connectors in the brake light harness using the circuit diagram, disconnect them, and check if the pins are loose or corroded; repair as necessary.
Finally, check the ground wire for the brake lights. The tail lights in a car typically share a single ground wire; if this ground wire is broken or poorly connected, the brake lights will not function. If issues are found, reconnect the ground wire.
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