Good points from Larry. A few more:

As a general rule when diagnosing electrical problems (even situations that result in smoke), check ALL your fuses before you start disassembling things. The brake light fuse is #2, a 10 amp fuse in a 86+ Vanagon.

Light bulbs can also act like fuses, and blow out when they receive too much current.

If I suspected that the wire was indeed burnt up after checking the fuses, I would test the continuity of ONLY the wire. Trace the wire from end to end, and disconnect it on both sides. Then check resistance of the wire. If you get no resistance, then your wire isn't blown. There may still be a short in the wire, but that's a different problem.

Electrical work of this sort is always tedious. 

-Jarrett

On Apr 8, 2014, at 8:00 AM, Larry Alofs <lalofs@GMAIL.COM> wrote:

>  More likely there is a short to ground in the wiring that leads to the
> brake lights or at the lights themselves.