tail lights wont work on 1995 GMC 2500 Pickup

i am having trouble with my tail lights i have changed the bulbs but they still not working. it started on the right side i got it to work then the turn signal stopped working with the lights on and now both sides r out i need help can anyone help ?

Asked by for the 1995 GMC 2500 Pickup
Hello it seems you may need to replace the headlight switch but i would recommend a diagnostic first.There is a repair center in Oakland that can perform a diagnostic on the electrical system.The name of the repair center is I.F.A. ask for Karl or Dana and they can fix the problem.HAVE A BLESS DAY from DR.RECO.