Why Do Fuses Keep Blowing?

[mick69]

Pls help, i am fitting a head unit in to my Yaris, but after i connect my new head unit to the existing power supply from the factory installed head unit and turn on the ignition, the fuse for the rear side lights blows making it illegal to drive on these dark winter nights, i have tried everything poss to rectify it but it keeps happening, any body got any idea how to get this sorted or do i go to an audio installer?

[armoredfist2002]

did you cut the wires for your head unit or did you use the iso adaptor.

if you cut any of the wires maybe one of them is not connected or touching somewhere