How do you get more power from a Fuse Box?
Sounds simple enough, until you look behind it.
Thankfully a lot of the empty relay slots have access to useful circuits.
Permanant live (AKA Circuit 30)
Relay 1 pin 2 (unfused)
Relay 2 Pin 2 (unfused)
Relay 5 pin 4 -via fuse 1 (radiator fan 30A)
Switched Live (AKA Circuit 15)
Relay 2 pin 4 (unfused)
Relay 3 Pin 5 (unfused)
Relay 4 Pin 4 (unfused)
Relay 6 pin 4 – via fuse 18 (various shit 10A or 15A)
Relay 7 pin 2 – this is acutally x-relief so goes off during cranking.
Relay 2 is mostly used by fuel pump relay, or carb manifold heater relay, but if you’ve got a conversion this may be free.
Relay 6 is for the dual horns, so poverty spec cars will just have a jumper.
Relay 7 is for front fogs, so if you’ve binned the lights, you can use the relay slot for something else.
The rest are mostly used, unless you don’t have wipers
Other useful stuff that appears on the empty relay slots are listed below:
Relay 2 pin 7 goes live when the starter is engaged.
Relay 2 pin 5 and Relay 4 pin 1 both have a strobed feed from the coil, good for aftermarket tachos or shift lights.
You can use the multiple earth points to the right of the fusebox for grounding all your electrical toys, but if you want more, here’s the earth connections for all the relays:
Relay 1 Pin 1
Relay 2 Pin 1
Relay 3 Pin 6
Relay 4 Pin 6
Relay 5 Pin 1
Relay 6 Pin 2 (not always connected)
Relay 7 Pin 1
Relay 8 Pin 1
Relay 10 pin 4
Relay 11 Pin 4
Relay 12 Pin 4
Obviously the last 4 or 5 won’t be available to you, unless you’re getting creative with the wiring.
Contributor: Forum user SkyRocketeer