I have 1999 toyota tacoma P/U. When my headlights are off my signal lights work fine. When my head lights are on my left signal stays lit up and my right signal works fine. Any suggestions.

If the head light switch/turn signals are in one assembly on the steering column its usually the switch has a short in it and the whole unit would have to be replaced

A faulty socket can cause this as well....check both the front and rear sockets