Phil,
The wire has to be of a certain rating... on my 400F (if I remember correctly) the indicators are on a 15A circuit / fuse. In other words, for the wiring to be adequately protected... it has to be of a rating greater than 15A. (If not, it'll 'fail' long before the fuse lets go...& give you headaches finding the fault)
So, can I suggest you simply buy your wire according to the rating, ie go for something 15A or greater.
The below might help... though you may likely find thinner 15A cable elsewhere.
Simon.