10 amps added load is not a lot. The fuse box "should" handle it. That said, the OE system is marginal especially the power feed to the fuse block. The system would be meaningfully more reliable and safer with a relay pulling power directly from the engine compartment. You still need a breaker or fuse on the feed to the relay.. Normally sized at least 25% higher than the load. 15 amp fuse for a 10 amp load would be OK I think.