I have ecountered a problem with my truck, no left side tail light, but the signals and brake light still work. It operates off of the same bulb but I can't find the culprit. It is probably staring me right in the face and just can't see if.
Just hoping that someone else knows what the quick fix

 

Its the same bulb but that bulb has 2 differant filiments in it , 1 brighter for brake & turn , the other dimmer for tail lt.
sometimes looking at the bulb you can not see a burnt filiment , while holding bace with one hand , tap the bulb with finger nail , and you should see the filiment wiggle .
When you pull the bulb , look into the bace [ truck end ] you'll see 2 metal nubs off to either side , those are the positives for either curcit , the outside metal coller is the negitive for both , carefully put a test lite on both of the center contacts to look for power with either light on , put a pice of tape around the shaft of the test lite as to not contacted the ground .
This should get you in the right direction , bulb/ truck.

 

Thanks.... I have tried different bulbs, I am sure that it is the truck...just don't know what/where.
Thanks.

 

Its comin to lose it at the splice for the trailer , especaly if its been done after market.
Other wize a lest lite again and follow the harness to the front , find a wiring diagram , with those 2 you'll be in the ame boat as the experts , finding and open curcit can be just a hunt & peck till you find it .