its a good indication,as some electrics need a ground earth and some need to be looped to make a pure circuit!

its usually a problem when fitting a stereo with no "distructions",as you usually go by the rule of earthing to the body earth,and then probs arrise,

where, as if , "we" follow the instructions after such a prob,it reads,"DONT EARTH ON CHASSIS!" then your king dick coz you took twice as long as it woulda in the first place ,but you fixed your motor!

it could just be a few amps,but its not good,as there will be a conflict,and burninig wires/loom shite, so get it sorted ,cos stripping out your motor and replacing the loom is horrible!

and we dont want that!