Originally Posted by jcartaya94
Doesn't the Add-A-Circuit split that power source into 2 circuits that function individually?
Note I won't be running anything high amperage, just GPS and radar detector.
Depends on how you insert it. The leg of the AAC without the wire goes to both fuses and should be the power supply. The leg with the wire is the split: the lower circuit is what you plug the stock fuse into, the top one has the wire and is what you hook up to your new accessory or circuit.
If you hook it up in reverse the new circuit will have to travel through both fuses. So long as the new one is lower than the stock fuse then the stock fuse probably won't blow, but it could under unusual circumstances.
In either case, the power supply wire to the stock fuse has to be able to carry the power for both circuits safely.
One thing you can do to ensure you have no issues is to use the stock power only as a trigger for a relay, then hook the relay up to the battery using an appropriate fuse. The benefit is that the circuit will be switched by the relay and not the stock system, and the stock power supply wire won't have to carry anything more than a small extra amount that any circuit can handle.