Chosen Solution
Ok so I’ve changed my break light switch signal light switch and every relay still when I apply my brakes my. Left turn signal stops blinking also my third brake light flashes when I turn on left turn signal
Sounds like the third brake light is shorted to the left brake/turn light. Try removing the bulb in the third brake light and see what effect that has. If your directional lights and brake lights work normally then, I think that short is the problem. The short could occur in the switching system itself or in the wiring to the lamps. Sometimes these circuits are load sensitive, meaning if a circuit is intended to operate one lamp and it tries to do more or less, it probably will produce some odd symptoms. The switching occurs at the directional turn signal lever location and your brake switch. I hope this gives you some leads.
@afifield , Ash. Check for corroded connections in taillight wiring especially all grounds for damage/pinched and corrosion(remove ground bolts/screws/connections) clean and tighten. Also look at all the bulbs and sockets for burnt/corrosion,etc.. If you have a trailer light hook up try removing the harness as they can cause light issues when the converter in the harness is faulty which happens often. Good luck. I hope this helped you out, if so let me know by pressing the helpful button.
