1. Bulbs: This is the most common cause. The brake light bulbs can simply burn out. Check both the center high-mounted brake light (CHMSL, also known as the third brake light) and the two brake lights on the rear. Replace any that are burnt out.
2. Fuses: Blown fuses are another frequent culprit. Consult your owner's manual to locate the fuse box and identify the fuses responsible for the brake lights. A visual inspection should reveal a blown fuse (a broken filament). Replace any blown fuses with the correct amperage. *Be cautious when working with fuses and electrical components.*
3. Brake Light Switch: This switch is located near the brake pedal and activates the brake lights when the pedal is depressed. A faulty switch can prevent the lights from working. It's relatively inexpensive and easy to replace, but testing it (with a multimeter) is needed to confirm its failure.
4. Wiring: Damaged, corroded, or loose wiring can interrupt the electrical signal to the brake lights. Inspect the wiring harness running from the brake light switch to the rear lights, paying close attention to connections and areas prone to wear. This can be challenging and often requires some electrical knowledge.
5. Brake Light Circuit Board (if equipped): Some vehicles have a circuit board for the brake lights. If there is a problem with the circuit board it can prevent the lights from working. It would require replacement and is less common but possible.
6. Relay (Less common): Some systems may use a relay. A faulty relay could prevent the brake lights from working. Again, testing is needed with a multimeter.
7. Grounding Issues: A poor ground connection can prevent the lights from working correctly. Check for corrosion or loose connections on the ground wires.
Troubleshooting Steps:
1. Check the Bulbs: This is the easiest and fastest thing to check first.
2. Check the Fuses: If the bulbs are good, check the appropriate fuses.
3. Test the Brake Light Switch: This is the next most likely culprit. A simple multimeter test can determine its functionality.
4. Inspect the Wiring: Visually inspect the wiring for any damage or loose connections.
If you're not comfortable working on car electrical systems, it's best to take your Blazer to a qualified mechanic. Incorrectly diagnosing and repairing electrical issues can lead to further damage.
