you have asked the question about relays. i will draw a diagram too , but jut to make it clear, a 4 pin relay has 4 wires, 1. output, 2, input, 3. signal wire 4. signal wire B. the relay work signal wire circuit should be completed.,most of the electricians here when replacing or installing the relays they rely on +ve signal and the other wire is grounded without any fuse.. and from the factory most of the relays are controlled with a -ve signal and for the positive side they have is a fused connection +ve from the fuse-box. this is to prevent the possible fire that can be caused incase of a short circuit. i hope that makes things clear.
