Electrical Question

[rmrc51]

I just installed a PowerPlate from Electrical Connect which has it's own relay. The Power Plate is only hot when the ignition is turned on.

My question is this.

When I install a Light bar or other accessories (Air Horn) that have their own relay, do I just hook these other accessories up to the Power  Plate and do away with the relay that is included with the Light bar being that the Power Plate has its own relay?

[Gryphon Rider]

The purpose of relays is to use a low current circuit to switch a high current circuit.  From you description, your power plate is designed to prevent to power for your accessories from going through your ignition switch and/or 5A accessory terminals, but rather to be controlled by them.

Whether you need to use relays for your lights or horn depends on how you switch them.  If you want your lights (or horn, but I doubt it) to be always on when your ignition is on, then you don't need a second relay.  If you want to use an on/off switch and are confident your switch and wiring can handle the current, you don't need a second relay.  If you want the lights to go on and off with either your high or low beam headlight, or with small control wires or a low capacity switch, then your should put another relay in specifically to switch your lights.

The best and most common way to switch your horn is to run wires from the existing terminals near the old oem horn location, using them to switch a relay for your air horn.

[John U.]

I just installed the same power plate to organize the accessory wiring.  My highway lights as well as headlight are powered by relays triggered to the starter switch. So I have provided an independent hot wire to the relay from the power plate. This will prevent another switch meltdown. As Gryphon Rider said, unless your switch is robust enough, you need  a second relay.