Anyone have an idea on the third brake light? mine works intermittently, and it's hard to tell if it's on or off.

 

what year is it??

the newer mdx's have had some problems with brake light switches having to much resistance that it powers the normal brakes lights but not 3rd brake light.

the older mdx's have had problems with the wire getting cut in the rubber harness cover on the driver's side between the hatch and car body.

 

brake pedal position sensor. Its under the steering column. When you hit the break pedal in turns the switch on/off.
Its common on these models, esp 07+
Has your cruise control stopped working too?
Take off the trim panel and you should be able to see it. Its green/black/white.
Be VERY careful removing it.
Unplug and then twist to free it.

 

What does removing it do? Does it fix it?

 

Yes, the problem will no longer be intermittant.

 

Does that mean that the light will work or not? if you are unplugging it......it's like chopping off your finger if you have an ingrown nail.