Originally Posted by comajoe
OK you kinda lost me there until the last paragraph, but i think i see what your saying.....a 20A fuse in the add a fuse should do it? thanks
Run the aux lights on a dedicated fuse connected to the battery positive or to a high-current tap in the underhood fusebox.
The wire on the add-a-fuse is not going to be sufficient for a 20a circuit.
Each pair of lights (if you're running 100w) needs it's own relay.
Light ground to chassis.
Light hots to relay pin 30.
Fuseholder to relay pin 87
Other end of fuseholder to power source.
Relay pins 85 and 86 are the relay coil.
Connect one of them to the chassis.
Connect the other one to your switch.
You CAN connect more than one relay to the switch, if for example, you want to operate 4 100w lights from a single switch.
The other pin on the switch goes to the add-a-fuse under the dash.
This one can be connected to a circuit that is switched with the ignition or hot 24/7 (just don't forget to turn them off!)
You CAN feed multiple switches from a single add-a-fuse. Just keep in mind that the fuse is protecting the WIRING... not the device.
The wire needs to be sized properly to handle at a minimum 40% more than the load.
The fuse should be sized to no less than 20% more than the load.
Now... you can ignore this part, I'm including this for others:
You may have noticed that I recommend connecting the load to relay pin 30 and the power source to pin 87.
Why did I do this?
Because not all relays are 4-pin. Many (most in my area) are 5pin.
If the battery is connected to pin 30, the relay is switching it between pins 87 and 87a. When your switch is off, pin 87a is hot... 24/7.
If it is not properly insulated and protected, it CAN cause a short.
By connecting the battery to 87, and the load to 30, the relay is switching the LOAD between 87 and 87a. When the switch is off, the load is connected to 87a. BFD. 87a NEVER goes hot.
The standard convention of connecting the hot to pin 30 is because many applications will use the relay to switch the hot between two loads... such as low-beam/high-beam, or fog/driving.
Of course, if pin 87a is properly insulated and/or connected to a load, then it is perfectly safe.
Want to run fog lights and driving lights in compliance with the law, and only have to add one switch to your dash?
Run the switch to a relay as normal, then feed the output of that relay to pin 30 of a 2nd relay. Connect pin 87a to the fogs and pin 87 to the driving lights.
Now connect the coil of the 2nd relay across your high beam socket.
When the high beams are activated, the 2nd relay pulls in, kills the fogs, and activates the driving lights.