The left rear lights on my 1983 GMC truck do not work, but the front directional does. I have checked the fuses and all are OK. The front directional will flash fast for awhile and then slow. Any suggestions? Thanks!

Have you tried new bulbs? I mean 83, its due time for them... also make sure the fuses are seated good, in and out a couple times on the fuse.

Yes I tried a new bulb and replaced the fuse but thanks for the suggestion.

Check the ground at the taillight.