Electricians?

[Walker]

I'm putting in some lighted rocker switches for aux. lights, etc. . and need to know the right/best wiring scheme.



Rockers have 3 blades:

1. is ground

2. is load

3. is power



Which is battery supply power? Load or power? And isn't one just for "lighting" the rocker switch? If so, should/can that be powered from a source in the cab fuse box (if so what fuse should I use)?



Here's my plan:

For the switches - use a common (shared) wire for the ground under the dash somewhere, and also use a shared wire for the load/power (whichever is NOT the main battery power source), and then run individual fused relays and wires to each switch for the MAIN power coming from the battery, grounding each light to the chasis/frame somewhere.



Sound about right?

 

[illflem]

Since you only have three terminals your power terminal is the + switched to the load which also powers the light. Some switches have separate power for the lighting, it is a double pole switch then and will have three terminals plus ground. If you are using relays and separate fuses past the switch I see no reason not to use one common + power wire on all switches.

 

[Spooled-up]

Try this...

I bought some switches at a Western Star dealership that were lighted. They couldn't really tell me how to wire them because they came as replacements for the stock switches - no wiring diagrams.



My Dad's an electrician and he suggested that I take a 9 volt battery (the kind you'll find in a household smoke detector) and use it to figure out which + and - will power the backlighting in the switch.



As for the power source for the backlighting, I used the wire coming out of the back of the headlight switch that powers the marker lights. I cut and spliced my power wire into it. I can't remember which wire it is, but I just put up a post and someone checked their book and got me an answer quickly.



Good luck.

 

[Briar Hopper]

"load" is whatever item you're switching. A light is a load. But most switches for automotive applications, you can't run a heavy load through, which is where relays come into play. (a heavy load being something like KC HiLites, or PIAA driving lamps) Here's how I see it:

Fused power coming from the battery to the switch, connect it to the blade (properly termed: "terminal") marked "power". Run a wire from blade marked "load" to the coil side terminal of the relay. The other terminal off the coil, run a wire from it to ground.

Looking at the relay, find your "normally open" contacts. Run a fused wire from the battery to one of those contacts' terminals. Then a wire from the other contact terminal to the lights. The light housing in most cases serves as your ground, unless the light has 2 wires coming out of it. And the switches' built-in light requires no other connections, it gets it's power from what you just hooked to the "power" blade.

The relay is simply a "tougher" switch that can handle the heavy amps you're putting through it, you're switching the coil on and off to operate the relay's switch.

Hope this helps...

 

[Amianthus]

Briar's description of how to wire a relay is pretty good. I wouldn't use a switch for powering a load that is more than 75% of it's rated load. I've used switches in the past for powering stuff, and I've found the best way to make the switch last longer and to get cooler operation of the switch is to use a relay. Plus, relays allow you to use really low current switches (small) to power just about anything and they aren't as intrusive and cumbersome to deal with when you have more than one load you want to switch.



As a side note, remember to put the battery back in your smoke detector when you are finished. Check this thread for some other people you can talk to about switches.



https://www.turbodieselregister.com/forums/showthread.php?s=&threadid=6141&highlight=switches

 

[BK]

Seems all posted above gave straight answers.

The only other input I can add is that you also need to be aware of how the switches are rated.

The off road lights are considered and "inductive load". When 1st powered they draw a hugh amount of current for a few milli-seconds. Which if the switch is only rated for a resistive load, the light will fuse the switch contacts shut, regardless of how much you think you've derated the switch for your application.

The relays that most use from Bosch and the Bosch knock off from radio shack are rated for inductive loads.



So, your not sure about your switch or as mentioned above, dont feel like changing switched out ever so often, add a relay.

Plus you can save on running some big wire through your dash board and place the relay next to the load.