it's a bulb, one of mine goes off and on, more off lately, most likely just bulb dying (turn signal bulbs do the same thing) you can replace it with a LED or a bulb.
98.5 SVT
91 Escort GT (almost sold)
96 ATX Zetec (i brake to watch you swerve)
FS: SVT rear sway bar
WTB: Very cheap beater
CEG Dragon Run - October 13-15