2012 CX9 - 3rd Brake light not working
 

So my 3rd brake light stopped working. I never noticed, but dealer bright it to my attention that it needed to be replaced.

To save a little, I bought a replacement and changed it. Still didn't work.

I connected a 12V source directly to both lights and they both work. I checked wiring all the way down the side panel & nothing looks frayed or chewed up.

I stopped short of taking the whole back panel out though.

It has been suggested that I get a multimeter to test connection, so that'll be the next step.

If anyone has run into this issue, any help would be appreciated.

The third brake light on most all vehicle do not have a separate fuse so if the other brake lights are working then it is narrowed down to 3 things.
The connector
The leads
The bulb

All you will need a volt/ohm meter to test.
The bulb is easy enough and you already posted checking that.

The ground is easy because you can jump the lead and ground directly to the connector. If the bulb does not work the next which is the power lead. While the brakes pedal is being pushed and the other brake lights are working you should have power to the connector. If not, then you need to follow the connector wire back to where they "Y" or splice off from the main brake wire going to the other 2 brake lights. There is no easy way at this point to do this unless you want to skip and just run a new lead wire from the other working brake lights.

Hello, my high-mount brake light repair ended up being a bad brake switch (SWITCH, STOP LAMP. Part # L232-66-490A). Did not have to change the actual light (LAMP, STOP - HI.MOUNT.. Part # TD11-51-580C) but did it because I made the wrong assumption at the beginning. I also changed the cable (CORD, LAMP - HI.MOUNT SEAT. Part # TD11-51-571B). 1 hr of labor

Wouldn't a bad brake switch affect all the brake lights, not just the high mount?

Did you change the cable at the same time and do you think it was that instead?

I'm a novice with this. I can probably figure it, but what does jump the lead mean and how do I do it?

I thought so too but now I recall my stop signal bulbs on both tail lights worked too and that's how I incorrectly concluded the problem was the 3rd brake light. The stop signal bulbs on the tail lights were slightly dimmed which you as an owner would not generally notice since you don't see it. Unless someone who pays attention and compares it to another vehicle (CX-9) with their stop signal bulbs on (pressed brake pedal), it's hard to figure it out. That's how I messed up originally. My friend helped me diagnose the issue down to the brake switch and the cable but could not 100% pin it to either one of the 2. That's why, I bought both so I don't have to waste time and risk going to the dealer a 2nd time if it turned out to be the other part. We did not have to change the cable but I already had it and replaced it anyway.

That said, I could have potentially replaced only the brake switch (under steering wheel) but ended up replacing the 3rd brake light (originally) as well as the cable since I already had it and didn't feel like going back to the dealer to return it.

How did you diagnose?
Dying want to just throw parts at it

With multimeter if I remember correctly.......I already did the big spending (the actual 3rd brake light). The brake switch and cable were less than $50 together. I did not intentionally start replacing parts hoping to fix the issue. I just made the wrong assumption at the beginning.

Jump the lead mean to run a wire by-passing the original. In your case using a wire preferable with pin or alligator clamps create your own and direct ground lean.
chiman101 does not sound like your problem, his was a direct voltage draw in a switch that was failing. Even in his case you would still need test by way of a volt/ohm meter the voltage at the brake lights. They should all be the same voltage.

Based on your information you posted somewhere??? however, it is not your connector because you wrote checking the bulb and it was working!

Ok there really is not much ANYONE can tell your more than what has been already said in this thread and those other 2 your responded in about your third brake light! LOL

Not that it matters on my 2018 completely removed it because IMHO it along with the rear 3 head rest (also removed) unobstructed rear view mirror vison. Unplugging the harness going to the center brake light did not affect the taillight brake light in any way.


INVEST: 8.39 USD EIGHT DOLLARS and THIRTY NINE CENTS


https://cimg8.ibsrv.net/gimg/www.maz...588fb8f3ef.png

Better late than never.

So I got a multimeter to test, but figured I'd give the brake switch a shot. Changed it out in 5 minutes and now my 3rd brake light is working great. My other brake lights actually got brighter as well. Turns out the 3rd brake light worked, it was just really really dim.