Fender mounted blinkers

Either something is not grounded, or you have wires in the harness crossed, that is, a turn line and a park or headlight line shorted together

With the problem "showing" clip your test lamp or meter probe to a good ground. Then 'stab' the other probe into the lamp socket shell.....that is, into the shell METAL HARD so the probe "gets through" rust, chrome, paint. If you get any voltage or a test lamp, the socket is not grounded.