3rd tail doesn't work but brake lights do

Maintenance/Repairs
,
1

Why does my 3rd tail light not work but my 3rd brake light does?

2

Did you check if the lamp is burned out?

Tester

1 Like
3

The third brake light is not used as a regular tail light, as near as I know. It only illuminates when the brakes are activated. There are normally only two rear tail lights, not three.

2 Likes
4

I may have worded that wrong.
3rd tail light doesn’t light up when head lights are on.
But lights up when brakes are applied.

5

CHMSL: Center High Mounted Stop Light

The center high mounted stop light is not a taillight, it only illuminates while braking.

6 Likes
6

What do you mean by 3rd tail light?

7

The center high mounted tail light

8

Unless you name a specific make year and model, I know of no car with a third tail light. The center high mounted brake light or lights only have a single filament bulb. Take the bulb out of yours. If it only has one contact on the center bottom of the bulb and one filament in the bulb, it is only a brake light.

9

It’s a Buick Enclave. Check the heading.

1 Like
10

NO center or 3rd tail light used that I have ever seen, only the 3rd brake light…

The purpose of the high mount brake light is to draw your attention to the person in front of you hitting their brakes, meaning it goes from no lights to very bright lights…
If there was already a light there, you might not notice it as much, that is a reason the 3rd brake light was made standard (required) equipment way back in 1986…

Tell me how many vehicles have you seen with factory installed 3rd tail lights???

1 Like
11

Did someone tell you that the High Center Brake Light was supposed to be on with the Headlights ?

12

This reminds me of a conversation that I had with an acquaintance, quite a few years ago. He was incensed that “two of the tail lights on my new car don’t work”. The " tail lights" were actually reflectors.

Unless the OP–or someone else–can give us proof that the center brake light on Buick Enclaves is also supposed to function as a tail light, I think we have to conclude that the OP is uninformed/misinformed, or confused.

1 Like
13

Perhaps a Video might “enlighten” the OP on the functions of the Brake and Tail Lights…

1 Like
14

See section S6.1.1.2 of the linked federal regulation regarding automobile lamps. It defines high mounted stop lamps. Tail lamps are defined elsewhere.

1 Like
15

There is no center high mounted tail light. It is a center high mounted BRAKE light. It only comes on when the car is braking.

2 Likes
16

It is not supposed to come on as a tail light for safety reasons. Before the center brake light became required equipment, rear end collisions were a lot more common. On reason (of many) is that if the driver following did not happen to be looking at the tail lights just as the driver stepped on the brakes and then noticed they got brighter, that driver would not realize as quickly that the brakes on the leading car were on.

Now if you are the following driver and are momentarily distracted/checking rear view mirror etc. and the leading car has applied the brakes, you will much more quickly notice three lights vs. two and know that you need to take action ASAP.

There are fewer rear end collisions today than before the center brake lights.

3 Likes