2001 corolla turn signal

I just bought a 2001 corolla, and the driverside front turn signal is not working right. the turn signal and the running light are both using the same fillament of the bulb. this means some where the turn signal wire is crossing over into the running light wire, or visa versa. when I have my head lights or running lights on the and go to use my signal it blinks rapidly as if the bulb is blown. I thought the bulb might be blown but I found out that was not the problem.

Does any one know where I should begin?