http://s93057182.onlinehome.us/3rd B...t Bad Bulb.jpg

Another Link

I was going through cleaning all bulbs and sockets over the weekend, and found both my 3rd brake light bulbs were like this.
Last I looked they were normal, clear bulbs. Now they're all charred, to a point where they are black, and have a a brittle grey bubble in the middle of the bulb.

Anyone know what would cause this and what I can do to prevent it again?

 

Your link doesn't work. But they were probably just old. Mine was just replaced, but the bulb wasn't charred, the wires inside it were. But if they are relatively new bulbs, then I honestly don't know what to tell you.

 

The links worked fine for me. As for the bulbs, looks like heat damage.

 

looks alot like heat damage (basically they are really old) or what a bulb looks like after it blows.. i have had lots of them look like that when they blow out.

 

I had one that the whole bulb was black but it still worked. I changed it anyway.

 

Its normal for an old bulb to get like that, its nothing to worry about.