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I need some advice from an electrical guru.


YamaDuck

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I need some advice from an electrical guru. I am trying to put passing lights on my 2001 RSV. I want to use a relay however the passing lights are for a Road Star. In the alternate wiring diagram the power goes from the positive side of the battery through a fuse to #30 on the relay. From there the power goes from #87 to the positive side of the passing lights. #85 on the relay goes to ground and #86 goes through a switch and is connected to one of the 3 wires going to the headlight. Red with a yellow strip if I want the passing lights on all the time (as I do).

 

My headlight does not have a red with a yellow strip wire. Problem #2. My passing lights have a switch built into the left passing light and the power (positive) goes through the switch. The right passing light has a red wire with a yellow strip. The left passing light has a red wire with a yellow strip and a plain red wire. I have connected the red wires with a yellow strip together with a wire running between the two lights. The left passing light has the red wire and the red wire with a yellow strip both connected to the switch. I have connected the red wire to another red wire that will go to the relay. The alternate wiring diagram shows the switch on the negative side. Is there anyway to connect the relay show that the switch is on the positive side.

 

Any and all help would be greatly appreciated.

Thanks,

Harry

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Actualy, I sort of prefer switching the ground side instead of the hot side as it eliminates the possibility of 12 volts to and from the switch accidently getting shorted to ground somehow, but that's my preference...

 

The main idea is the switch turns the relay on or off, which uses a small amount of current. Let the relay handle the big amount of current that the lights use, they are designed for that! Switches burn out in short order if they have to pass too much current.

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It really doesn't matter if the switch to energize a relay is on the positive or negative side of the relay. It's still going to be passing the same small amount of current.

 

What does the most damage to switches is the arcing that occurs when the switches are opened and closed with a load attached. You can see what I'm talking about when you connect or disconnect a battery lead. You'll see a small arc shoot from the lead to the battery terminal. Over time, this chars and corrodes the contact points in the switch until they no longer conduct. The bigger the load, the more arcing and damage occurs.

 

When you turn on the ignition switch, there is 12v on one side and a bunch of loads on the other - lights, fuel pump, gauges, etc. So, there's a bit of arcing that occurs inside the ignition switch. Apparently, the additional load from passing lights is enough, over time, to damage the contacts so bad they quit working.

 

In your case, you have a switch on the passing lights to turn them on and off. That switch is probably not going to be used much, and only has the load of the passing lights going through it. So, I would leave that switch in place, as-is.

 

This is what I would recommend in your case, to keep things very simple:

- Tie into the 12v lead from the cigarette lighter plug, and use that to close the relay (terminal 85). It's switched, meaning it's only on when the ignition is on.

- Ground the other side of the relay (terminal 86) to the side of the radio. There's already a bolt and large ground wire going to it. Use that same bolt.

- Take the red lead from your passing light on/off switch and run it to terminal 87 of the relay.

- Run 12v from the battery (with a fuse, of course) to terminal 30 of the relay.

 

This will take the passing light current out of the ignition switch, which is the primary reason for the relay. It will keep the wiring as simple as possible. And you will have a way to turn off your passing lights, if needed.

 

Hope this helps.

 

:)

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I think most of us are using the standard 30A relays available at most auto parts stores for ~$7.

Thanks Michael. Explained so well even a cave man can do it. Yes I'm using a 30 amp relay with 4 prongs #30, #85, #86, and # 87. Got it at the auto supply store $7.49 plus tax.:thumbsup2:

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Thank you atlm,I assume you are running that trough a 30a fuse. I'll stop by napa today on my morning ride and pick one up and get this project taken care of. Do not want to loose the ignition. Thanks again.

 

Richard

 

For the passing lights, I'm using a 10a fuse. That's enough for 120 watts (12v x 10a). If your passing lights have high wattage bulbs, like 55w each, you could go with 15a.

 

With the tiny wires used for the passing lights, I prefer a small fuse. In the event of an issue, I want the fuse to blow quickly, rather than have a short or partial short fry the tiny wires.

 

:)

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