The 12v feed for the solenoid on the starter comes direct from the igntion switch, via a black/blue wire, there is also another black/blue wire of the same size that goes to the fusebox, so don't confuse the two if tracing wire, not that there's any need, as you have 12v, your best bet would be to get an assistant, turn the key etc, whilst you put your finger on top of the relays in the fusebox, to see which one, if any in here is clicking.
tabetha