Third BRAKE light stopped working

[jhilario72]

On my 2003 Denali XL, I noticed that the third break light stopped illuminating when breaks are applied. The normal break lights go on. Is there a fuse or something that controls the third break light? Or is it a single bulb that burned out?

Thanks!

 

[gooffeyguy]

Probably burnt out. The one on my 2001 has before and the entire red plastic lens/housing gets replaced and just plugs in back behind it

 

[OR VietVet]

No separate fuse. Replace the whole thing. Easy to get to and check power and ground.

 

[Fless]

Contrary to what you've heard, there's a fuse for it in the in-cab lefthand fusebox (VEH CHMSL):

 

[OR VietVet]

Contrary to what you've heard, there's a fuse for it in the in-cab lefthand fusebox (VEH CHMSL):

View attachment 416822

That's not for the 3rd brake light. That is for "Chair Heat Module Seat or Leg". Everyone knows that!!!!!

 

[OR VietVet]

If the CHMSL stands for "Chassis mount stop light". Aren't they all chassis mount? Please break down the CHMSL, thanks.

 

[Fless]

If the CHMSL stands for "Chassis mount stop light". Aren't they all chassis mount? Please break down the CHMSL, thanks.

Center High-Mounted Stoplamp

 

[OR VietVet]

Center High-Mounted Stoplamp

View attachment 416836

Ok, ok, ya got me. I effffed up. I am going to my room now.....

 

[ScottyBoy]

When my 3rd brake light went out, I unhooked it and checked the voltage at the plug while I had a helper press the brakes. I did indeed have voltage, so I just ordered a new 3rd brake light from Amazon. I don't believe they have a replaceable bulb, I think you do indeed HAVE to replace the entire housing. It was only about $20-$25 it wasn't expensive at all.

 

[mwilson62000]

Does your cruise control still work? If I remember correctly, years ago in my Tahoe, the CHMSL stopped working and I happened to notice my cruise wasn’t working either. Was the brake light switch under the dash.