In theory, yes, however it would be advisable to look up whichever
manufacturer the radio is and check the current rating for that line.

Sony supply good information regarding their stereos, as do Pioneer.

The last thing I would add, does the line have a fuse inline, if so check
it's rating, that will let you know an upper limit and say anything 10% and
maybe even as much as 70% below that would be the answer.

Paul