1990 Volvo 760 wagon horns on 1990 Volvo 760

Why my 1990 Volvo 760 wagon horns' one pole directed ground other than as Chassis Schematic showing? The horns didn't work except little sound. Is it due to the relay function? No problem had been found with fuse and the horn after my checking.

Asked by for the 1990 Volvo 760