if it is on a mk3 the brown and red goes to the fuse box then a feed comes off for the stereo you could cut out the burnt wire because now its got hot it will be a week point in the circuit cut out solder in new bit the same thickness but make sure you get some heat shrink to cover where you soldered or better get back to the fitter he does`nt realy have a leg to stand on his c**k up his prob rearlly