# 3rd tail doesn't work but brake lights do **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** enclave, buick\ **Created:** [February 8, 2025, 3:37am UTC](https://community.cartalk.com/t/3rd-tail-doesnt-work-but-brake-lights-do/199029 "2025-02-08T03:37:51Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![I.am9010](https://avatars.discourse-cdn.com/v4/letter/i/fbc32d/32.png) [@I.am9010](https://community.cartalk.com/u/I.am9010)\ **Post date:** [February 8, 2025, 3:37am UTC](https://community.cartalk.com/t/3rd-tail-doesnt-work-but-brake-lights-do/199029/1 "2025-02-08T03:37:51Z")
Why does my 3rd tail light not work but my 3rd brake light does? ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [February 8, 2025, 3:49am UTC](https://community.cartalk.com/t/3rd-tail-doesnt-work-but-brake-lights-do/199029/2 "2025-02-08T03:49:24Z")
Did you check if the lamp is burned out? Tester ---
**Author:** ![jdmere](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/jdmere/32/3002_2.png) [@jdmere](https://community.cartalk.com/u/jdmere)\ **Post date:** [February 8, 2025, 4:32am UTC](https://community.cartalk.com/t/3rd-tail-doesnt-work-but-brake-lights-do/199029/3 "2025-02-08T04:32:16Z")
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. ---
**Author:** ![I.am9010](https://avatars.discourse-cdn.com/v4/letter/i/fbc32d/32.png) [@I.am9010](https://community.cartalk.com/u/I.am9010)\ **Post date:** [February 8, 2025, 4:52am UTC](https://community.cartalk.com/t/3rd-tail-doesnt-work-but-brake-lights-do/199029/4 "2025-02-08T04:52:53Z")
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. ---
**Author:** ![Nevada\_545](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nevada_545/32/41232_2.png) [@Nevada\_545](https://community.cartalk.com/u/Nevada_545)\ **Post date:** [February 8, 2025, 5:14am UTC](https://community.cartalk.com/t/3rd-tail-doesnt-work-but-brake-lights-do/199029/5 "2025-02-08T05:14:35Z")
CHMSL: Center High Mounted Stop Light The center high mounted stop light is not a taillight, it only illuminates while braking. ---
**Author:** ![asemaster](https://avatars.discourse-cdn.com/v4/letter/a/5f9b8f/32.png) [@asemaster](https://community.cartalk.com/u/asemaster)\ **Post date:** [February 8, 2025, 5:53am UTC](https://community.cartalk.com/t/3rd-tail-doesnt-work-but-brake-lights-do/199029/6 "2025-02-08T05:53:05Z")
> [@I.am9010](#): > > 3rd tail light doesn’t light up when head lights are on. What do you mean by 3rd tail light? ---
**Author:** ![I.am9010](https://avatars.discourse-cdn.com/v4/letter/i/fbc32d/32.png) [@I.am9010](https://community.cartalk.com/u/I.am9010)\ **Post date:** [February 8, 2025, 5:57am UTC](https://community.cartalk.com/t/3rd-tail-doesnt-work-but-brake-lights-do/199029/7 "2025-02-08T05:57:57Z")
The center high mounted tail light ---
**Author:** ![oldtimer-11](https://avatars.discourse-cdn.com/v4/letter/o/e79b87/32.png) [@oldtimer-11](https://community.cartalk.com/u/oldtimer-11)\ **Post date:** [February 8, 2025, 10:24am UTC](https://community.cartalk.com/t/3rd-tail-doesnt-work-but-brake-lights-do/199029/8 "2025-02-08T10:24:57Z")
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. ---
**Author:** ![jtsanders](https://avatars.discourse-cdn.com/v4/letter/j/c2a13f/32.png) [@jtsanders](https://community.cartalk.com/u/jtsanders)\ **Post date:** [February 8, 2025, 1:17pm UTC](https://community.cartalk.com/t/3rd-tail-doesnt-work-but-brake-lights-do/199029/9 "2025-02-08T13:17:06Z")
It’s a Buick Enclave. Check the heading. ---
**Author:** ![davesmopar](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/davesmopar/32/41750_2.png) [@davesmopar](https://community.cartalk.com/u/davesmopar)\ **Post date:** [February 8, 2025, 2:39pm UTC](https://community.cartalk.com/t/3rd-tail-doesnt-work-but-brake-lights-do/199029/10 "2025-02-08T14:39:43Z")
> [@I.am9010](#): > > Why does my 3rd tail light not work but my 3rd brake light does? 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??? ---
**Author:** ![VOLVO-V70](https://avatars.discourse-cdn.com/v4/letter/v/8e8cbc/32.png) [@VOLVO-V70](https://community.cartalk.com/u/VOLVO-V70)\ **Post date:** [February 8, 2025, 2:46pm UTC](https://community.cartalk.com/t/3rd-tail-doesnt-work-but-brake-lights-do/199029/11 "2025-02-08T14:46:52Z")
> [@I.am9010](#): > > 3rd tail light doesn’t light up when head lights are on. > But lights up when brakes are applied. Did someone tell you that the High Center Brake Light was supposed to be on with the Headlights ? ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [February 8, 2025, 3:11pm UTC](https://community.cartalk.com/t/3rd-tail-doesnt-work-but-brake-lights-do/199029/12 "2025-02-08T15:11:08Z")
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. ---
**Author:** ![LoudThunder](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/loudthunder/32/27769_2.png) [@LoudThunder](https://community.cartalk.com/u/LoudThunder)\ **Post date:** [February 8, 2025, 3:32pm UTC](https://community.cartalk.com/t/3rd-tail-doesnt-work-but-brake-lights-do/199029/13 "2025-02-08T15:32:24Z")
Perhaps a Video might “enlighten” the OP on the functions of the Brake and Tail Lights… [![](https://global.discourse-cdn.com/cartalk/original/3X/f/0/f0dddd86d731927dd4358f4738d0879a4e87e55d.jpeg "Brake Lights vs Tail Lights - What's the Difference? (Are They the Same Bulb?)") ](https://www.youtube.com/watch?v=M-A-rG_BXAk) ---
**Author:** ![jtsanders](https://avatars.discourse-cdn.com/v4/letter/j/c2a13f/32.png) [@jtsanders](https://community.cartalk.com/u/jtsanders)\ **Post date:** [February 8, 2025, 4:56pm UTC](https://community.cartalk.com/t/3rd-tail-doesnt-work-but-brake-lights-do/199029/14 "2025-02-08T16:56:17Z")
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. > **[49 CFR § 571.108 - Standard No. 108; Lamps, reflective devices, and...](https://www.law.cornell.edu/cfr/text/49/571.108)** ---
**Author:** ![asemaster](https://avatars.discourse-cdn.com/v4/letter/a/5f9b8f/32.png) [@asemaster](https://community.cartalk.com/u/asemaster)\ **Post date:** [February 8, 2025, 4:58pm UTC](https://community.cartalk.com/t/3rd-tail-doesnt-work-but-brake-lights-do/199029/15 "2025-02-08T16:58:34Z")
> [@I.am9010](#): > > The center high mounted tail light 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. ---
**Author:** ![keith](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/keith/32/5518_2.png) [@keith](https://community.cartalk.com/u/keith)\ **Post date:** [February 9, 2025, 3:41am UTC](https://community.cartalk.com/t/3rd-tail-doesnt-work-but-brake-lights-do/199029/16 "2025-02-09T03:41:00Z")
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.