replace the bulb..1.00$ FTW if it doesnt fix it your looking for a moisture problem, somethings "shorting" it out and not letting it work, or if you really want..
using the bulb that wont work, unplug it, grab a test light and leave your signal on, put the test light on either pin and if it lights up on one and flashes its working at the connector and the bulb is toast..NOW if it doesnt work then the problem could be farther down the line..check the wiring..not that hard to find might have to play detective!
89 S-10 Blazer- SOLD
00 Honda Civic- too many mods to list..mm turbo..
01 Acura EL 1.7- SOLD
02 Edge 3.0 - SOLD
03 FX4 Level II - SOLD
03 PSD lariat 7.3L- Written off ( RIP 03/15/09 )
03 PSD lariat 7.3L- bought 04/06/09