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Fuse Block and Relay Installation

8/15/2010

As we already mentioned in our " Motorcycle Fuse Block Installation " article, there are a couple popular ways of wiring up accessories to your bike through a fuse block. And, like almost everything else, there are various methods of wiring the fuse blocks to the motorcycle.

In the first article we covered the simplest form of wiring the fuseblock to the bike. This was accomplished by wiring the positive and negative of the fuse blocks directly to the positive and negative of the battery. While this method is an effective way to get the job done, it also makes it easier for you to drain the battery if you leave an accessory on. The reason for this is that there is no On-Off switch to tell your fuse block to stop providing power to the accessories.I've personally had to bump start my bike because I left my GPS on for a couple days in a row without riding the bike.

An easy way to get your fuse block to turn on and off is to install a relay between it and the battery. If you aren't familiar with the how's and what's of a relay take a look at " Using a relay for your accessories " .

Basically the way it works is that you wire up a relay between the battery and the fuse block and use a circuit on the bike that is live only when the key is turned on to trip the relay. That switched circuit energizes the relay whenever the ignition is on, thereby allowing power to flow from the battery to the fuse block. These switched power sources vary from bike to bike but some examples of these might be low beam, running light, tail light, and factory accessory sockets.

The wiring of a relay into the fuse block circuit is relatively straightforward. The trickiest part can be finding and accessing a switched ciruit to use. What you are looking for is a circuit that is on when the key is on and off when the key is off. As a general rule I try to find a circuit that isn't critical to the bikes operation. By that I mean that if I have a choice between a tail light and an ABS circuit I'm going to pick the tail light.

Here are some examples of connectors that you can use to help tap into an existing circuit to get switched power back to your relay.

Tap Splice
Posi-Tap
Fuse Tap
Spade Splitter
Tap Splice
Posi-Tap
Fuse Tap
Spade Splitter
Taps existing wire
Taps existing wire
Taps existing fuse
Taps existing spade connector

 



Fuse Block & Ground Block wiring

When wiring up a system that is using a power block and a seperate ground block you still wire the ground block directly to the battery. Your power block is where you are going to place the relay for your system.

In our example the role each relay connector plays is listed below:

  • 30 - This is the power coming from the battery
  • 85 - This is the ground for the relay
  • 86 - This is the circuit that will activate the relay. When this circuit is energized the relay is triggered and power is sent to the output pin of the relay.
  • 87 - This is the power output pin and it is what you use to feed the fuse block.

Note: Remember that relays come in many styles so verify the connector layout of your relay before wiring it up.

If your power block is more than a couple inches away from your battery connection I recommend an inline fuse close to the battery, before the relay. This will help protect your wiring should your power wire short out for some reason.

This brings me to another point. Zip Ties are your friends. Wires that are left loose have a greater chance of wearing through the insulation and shorting out. If you secure your wires to something like a factory wiring harness or frame rail you will reduce your chances of chaffing and wearing through the insulation.

Once your fuse and ground block are wired up all you have to do is route the power and ground wire from your accessory to the appropriate block, connect them, and again secure them to reduce the chances of chaffing.



When wiring up a system that has the power and ground block on one device you still wire the ground block directly to the battery. Your power feed for the fuse block is again where you are going to place the relay for your system.

Just like the earlier example of wiring a separate power and ground block, wiring something like the Blue Sea or the Centech fuse blocks to your bike is a pretty straight forward process. Both of these units have a power and a ground lug incorporated into the design so you simply take your ground from the battery and place the relay on the power side between the battery and fuse block as described above.

In our example the role each relay connector plays is listed below:

  • 30 - This is the power coming from the battery
  • 85 - This is the ground for the relay
  • 86 - This is the circuit that will activate the relay. When this circuit is energized the relay is triggered and power is sent to the output pin of the relay.
  • 87 - This is the power output pin and it is what you use to feed the fuse block.

Note: Remember that relays come in many styles so verify the connector layout of your relay before wiring it up.

Once your fuse block is wired up all you have to do is route the power and ground wire from your accessory to your fuse block, connect them, and again secure them to reduce the chances of chaffing.

Fuse Block & Ground Block wiring


However you decide to wire up your fuse block it's a good idea to roughly run the wires, make your connections, and test the circuit before your final installation. From experience I can tell you it's no fun to run wires under tanks and along frame rails and then find out that your inital plan needs a little refining.

That's it, you've just wired up a fuse block to your bike that will turn on when the key is on and will turn off when the key is off.

Below is a listing of the fuse blocks we carry. The Centech AP-2 is a hybrid fuse block and it enables you to power accessories that are on all the time and ones that are switched with a relay. This is a great setup if you are looking to do something like have a GPS that is on all the time and a set of driving lights that is on only when the bike is on.

Model
Dimensions
Circuits
Ground Bus
Terminal Location
Blue Sea 5025 4.9" x 3.32" x 1.52"
6
Y
Internal
Centech AP-1 3" x 2.4" x 1.25"
8
Y
Internal
Centech AP-2 3" x 2.4" x 1.25"
8
Y
Internal
Centech FB-4 3.5" x 1.75" x 1.5"
4
N
Side
Centech FB-6 4" x 1.75" x 1.5"
6
N
Side
Powerlet PMI-002 & PMI-019 2.5" x 1" x 2"
4
N
Raised Bottom
Fuzeblock FZ-1 3.25" x 2.5" x 1.25"
6
Y
Side

Various Fuse Block Spec's

If you are interested in learning more about basic troubleshooting and repair of your bikes electrical systems there is a very good book that you might want to add to your collection appropriately called Motorcycle Electrical Systems Troubleshooting and Repair .