I noticed my left light wouldn't come on, so I got me a pair of new bulbs and ran with the same issue.... Only the left light comes on, I swapped the bulbs with same results. I pulled my multimeter and check voltage on the red/green wire with optimum results. There are other 3 wires that aren't drawing any voltage..... Are those for ground only?. Any assistance will be appreciated.

 

Regular bulbs or led? LEDs only work one way soy you might just have to flip them over to reverse the polarity. Otherwise maybe it's just a loose connection? Try tweaking the contacts a bit with a pick or small screwdriver maybe you'll have success.