The brake lights on your Volkswagen are part of the safety equipment, and they alert drivers behind you that you intend to stop. Should they stop working, you put yourself at risk for a rear end collision, so any malfunction of the brake lights needs to be addressed immediately.
- Volt ohmmeter or LED test light
When you use a volt or test light, make sure that you use them properly. The point on the tool needs to touch the contact point only during testing. If you push the probe into a socket, it can cause failure of the socket due to the spreading of the contacts.
Brake Lights Stay Lit
There are only a few reasons that would cause the brake lights to stay lit.
Bad brake-light switch – Should the contacts stick, the power may stay on even when released. You can test the switch before you replace it. An analog switch is simple, but if your vehicle uses a digital sensor instead of a switch, you may need to seek the help of your local dealership.
Analog light testing is done by removing the brake light switch and checking the continuity between its terminals. You need an ohmmeter and the wiring diagram. Check the wiring diagram to see which terminals you need to check.
If you only have two terminals, the continuity will be in one position and the open circuit will be the opposite. If you have more than one terminal, use your wiring diagram to determine which numbers or colors to check.
Use the wiring diagram to determine which leads need to have continuity and when they need it. A brake lamp part of the switch will need continuity when the brake has been depressed. The release of the brake pedal returns it back to the up position. When it is in the up position, the brake light switch then changes to an open circuit. Should you see continuity when it has been released or open when it should have continuity, then replace the switch.
In some cases, the brake pedal is failing to make contact with the switch. Your Volkswagen may have a small plastic pad at the switch attached to the pedal that connects with the switch. This plastic pad may break or become dislodged, which means the brake may not push the switch. This can cause light problems.
It is possible that the switch may have slipped out of position, which would increase the space between the pedal and the plunger. Check your pedal to make sure that it is making contact with the switch.
Brake booster – In some cases, the brake booster could be the problem due to failure. This means the pedal cannot raise high enough to make contact with the switch. Grab your brake pedal and pull it up. If the lights turn off, the switch is either misaligned or the pedal is in the wrong position.
Wire short – You may have a short in the wiring. You can check by unplugging the brake light switch and checking the lights. If they stay on, you have a short circuit somewhere. You may want to leave checking for the short to your local dealership.
Brake Lights Do Not Light Up
The first thing to check when your brake lights are not working is your third brake light. If it is also not functioning, then you could have a bad brake light switch, a blown fuse or your wiring harness has become unplugged. If your vehicle uses brake lights as your emergency flashers, you can test this by trying to use them.
If you see all the lights, and the emergency flashers are working, then all the bulbs, sockets and wiring are good. Check your owner’s manual to see where the fuses are for your brake lights and look for a blown fuse. If the fuses are good, you probably have a brake light switch that is bad. Using the instructions above, test your switch for continuity and replace it if it is bad.
Brake Lights Out, Third Light Works
You can rule out the brake light switch if your third light is working but the brake lights are not. Check the emergency lights to test the wiring, lights and sockets. If the flashers work, then test for a blown fuse.
If your Volkswagen uses the same lights for the turn signals and the brake lights, you may have a bad turn signal switch that is causing the lower brake lights to stop working. A bad turn signal switch will not affect the third light.
With this type of system, the turn signals use the same circuit as the brakes, which means that you cannot have both of them on at the same time. If the turn signal switch is bad, it can interrupt the brake light circuit. It can also be a broken wire on the switch that is causing the lights to stop working.
Lower Brake Lights Work, but Third Brake Light Does Not
If you see that the third brake light is the only one not working, try your emergency flashers. If the third brake light flashes, then most likely a fuse has gone bad. If it is not working with the flashers, then you may have a bad light or socket. Many of the newer third brake lights are LED, which means they do not have bulbs, and you need to replace the unit.
Brake Lights Only Out on One Side
If your brake lights are only out on one side, it is most likely that the bulb or the socket is bad. Turn on your emergency flashers. If there are no lights, it is the bulb or socket. Check the lights and replace a bad one.
If it is not the bulb, you will need to check the socket and connectors.
In order to check the sockets and connectors, you must first inspect the sockets for any type of corrosion, discoloration or distortion. Depress your brake pedal, and then use a voltmeter to touch the terminals lightly in order to check for voltage. If there is no voltage at the terminals, the wires in the socket need to be back-probed. Use a back probe adaptor and never a straight pin or anything that can damage the coating on the wires. Seal any area checked since damaged wires can cause problems for you later on.
If there is no voltage to the side that is not working, a broken connection or bad turn signal switch may be the cause. Voltage present between the ground and the wires means that the ground wire needs to be checked. Use the ohmmeter to check the continuity. If you have a good ground, then replace the socket. Make sure that you repair any insulation damaged.
If we assume that the red wire is the power lead to the brake lights, and the black wire is the ground, when we apply the brakes, the red wire should show current flowing through it. If you do not see this, then there is a problem with the circuit.
With your brakes applied, the ground should show less than 0.1 volts. More than that and you are showing high resistance in the circuit. If there is full voltage between the black wire and the ground, you have a broken or missing ground. Use the ohmmeter and check for continuity between the body ground and the black lead.
In order for you to find the broken circuit or bad connection, you need to use the wiring diagram. Start at one end of the circuit and look for voltage and ground. If it is not there, check the other end of the circuit. If there is ground and voltage, you need to check the middle of the circuit. If there is no power or ground, then the problem is in the first half of the circuit. Keep dividing the circuit in half until you find the problem.
While most brake light problems are relatively easy to find and correct, if you do run into problems, contact your local dealership for assistance.