How do i know if i have to replace the circuit board?
 

I have been having problems with my drivers side rear turn signal. Since i bought my 2004 jeep grand Cherokee. I have been replacing the bulb in my turn signal. Except ive been using the same 2 bulbs. They dont blow. If i just switch the bulb. It starts working again. Recently, its been the passenger turn signal and NOT the drivers side. My friend looked at it for me. He said it was a lose wire. He fixed it. Works great! NOW I have NO lights on my driver rear light. No break lights, no turn signal, no tail lights. I have changed the bulbs. Checked the connectors. Nothing! So do i need a whole new light? I need help..

I think you have a bad ground for the lights. That will start giving you crazy stuff like this. It will need to be re established. Also check the bulb contact points and make sure they are clean