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Vehicle Accessory Wiring
Okay so I've got a few accessories I need to connect to a switch panel. My problem comes in where I'm not sure what I need to protect it.

If I have a 20amp rocker switch and a 5a accessory running off it, do I need a breaker between the switch and battery? Or can I just connect the switch to battery and accessory to the switch?

I'm all set on grounding, just need to figure out how to power everything correctly.

Thanks in advance.

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In most any negative ground DC electrical circuit , you put the protection in the positive side as close to the source ( battery, load center, fuse block etc.) as possible.
Before the switch or the load it supplies.
What you are really protecting is the wire its self ,make sure your wire is larger Than it needs to be to carry the load , then size your breaker or fuse based on the wire size.
Ok so a switch saying it's rated at 20amps doesn't actually protect anything fuse would? Even with a 20amp switch I would still need a breaker greater than 5amps? I've got links to a couple examples a soon as I get a minute for a better visual.

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Ok so for a visual....

I'm also thinking i'm just not understanding why the switch says 5/10/15/20/etc amps on them if they still need a breaker or fuse....

Should I get one of these and run it to the battery then the accessories to the switches.

Or can i just get switches like these and run them to the battery and the accessories to the switch? Skipping the breakers.

Dorman Rockers

Carling Rockers
    Almost every electrical switch will have a rating,your switch has a 20 amp rating.
That means it can have up to 20 amps running through it without damage to the switch.
It does not mean it is a circuit protector.

Here is a wire chart for wire sizing
After rereading your links, the marine switch assembly on eBay does have built in circuit protection.
Just make sure your wire feeding this switch panel is protected.
If you take power from a load center/fuse block, it is most likely already protected by a fusible link.
But this protection may be at a higher amperage than you want .
If you run a wire straight from the positive battery terminal , then you have no protection.
Most automobile manufactures will only leave the battery cables unprotected, once that positive cable reaches the under hood load/fuse center the power is passed through large breakers, fuses, fusible links before it is passed on to the rest of the electrical system.

What type of vehicle are you working with?
Thanks man, your last two posts really helped. I thought the 20amp rating on the switches was a 20amp circuit/fuse protection. I guess ill just go with the marine switch panel with the breakers already pre-wired.

So if I have this right.....

I need a fuse or circuit between the switch panel and battery, then, i can just connect my accesssory power wires to the switches and ground each accessory.

You mentioned taking power from a load center. To test the accessories, I've unplugged my glove compartment light and just insert the +/- wires from the accessory. Could I hook the switch straight into the ground/power wire from the glove box light, since the glove box light runs to a fuse in the fuse panel?

Sorry if any of this sounds silly. I know how to connect and wire things up, just not sure of what i need to do this correctly.
A glove box light is probably on a low amp fuse with small wires.
The best place is probably the under hood fuse block
Some vehicles especially trucks and SUV's even have threaded studs that are already powered by fuses.
Having done a lot of radio installations in my time, the information you've gotten about fuses so far is decent. You're protecting against a short circuit and the entire frame of the vehicle is "ground" so any positive lead coming from a source needs to be protected in case the wire's insulation is rubbed away and the wire makes contact with any metal on the vehicle body.

As far as "where" to get power for accessories, that depends a lot on what you're hooking up. Using a switch rated at 20 Amps continuous is overkill for most accessories but will be plenty big for all but the biggest devices you'd probably see installed in a vehicle : Large stereo amplifiers, really big inverters, or high powered two way radio or lighting accessories.

What is the accessory you're planning to switch on and off with the switch?

Most vehicles have more than one circuit for "cigar lighters" for charging various gadgetry these days and if you don't plan on using those, you can tap those circuits or disconnect them and use them -- they're usually fused at either 10A or 15A already. Additionally most models have an unused "accessory" spot in their in-cab fusebox that can have a fuse added there and wires attached and run to the location of an accessory.

Barring all of that, there's also usually at least one grommet in the firewall that's just acting as a water intrusion plug and can be popped out and either have a small cut made in it so wiring can be run directly to the vehicle battery terminals and attached properly there (very common with two-way radio gear, since you're also trying to get low noise power and the battery acts as a big "capacitor", plus many large two way radios with high power needs don't like being fed through undersized wiring and the resulting resistance and voltage drop are both undesirable.

If all else fails and you're not electrically minded, any car stereo shop can point out good places to tap power from for in-cab accessories, or run you a nice set of cables properly from a high-current source location appropriate for the model from under the hood to a terminating block hidden somewhere inside the cab. They also have parts on hand like the replacement grommets that have a rubber boot and seal for passing wires through where a water plug was located from the factory in the firewall.

Really depends on what you're running as an accessory, but you should match the wire gauge properly for the current expected, and I've seen car stereo and two-way radio and inverter installations that needed 4 gauge cables directly from the battery system, dual batteries and an isolator so the car will still start if not running when the accessories are used, and an upgraded alternator capable of producing enough current to keep up with the accessory draw and still charge the battery when the engine is running. (Lighting can also draw enough power for this, also... But the advent of LED lighting has lessened that somewhat.) Then of course make sure you've fused it properly so the fuse goes before the proper cabling.
Denver Pilot, thanks for that well explained reply. I'm going to be wiring strobe and flashing lights up for security.

I'm planning to have 6 sets of 5 of which are only 2.5a a piece. Each set of lights will have it's own switch. They're cheap ebay LEDs so they each have their own controller that will be constant on, using the switches to supply the actual power.
The 6th set of lights I believe is 5a. So I'll have a total of 17.5a running through the switch panel with all the lights on, and 2.5-5a running through each switch.

Hope these details help to reveal more info.

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All sounds do-able. 17.5A you're going to want a dedicated circuit from either the under-hood fuse block or a dedicated 20A location provided by the vehicle manufacturer. (You'll have to talk to someone with access to the service manual or a radio shop to find out if a specific vehicle has such a location already wired in the interior.)

I've run some big stuff (6 and 8 gauge) direct off of the battery terminals before through firewalls at an available grommet opening with proper rubber strain relief grommet there and then to a distribution point inside the interior, usually tucked away up behind the dash. On one of them, the whole thing needed to be removable so a large PowerPole connector like you see on cop cars for their external "plug" for jumper cables, was what it terminated in, inside, and then the same plug on a distribution panel that could just lie on the floor and have other things plugged into it (also via smaller Anderson powerpoles) and all of those were individually fused for the things plugged into them.

I'm sure you realize this, but make sure to check your jurisdiction for use of strobes and flashers. Usually white and amber are allowable but not in motion. Anything else for colors and you can often be cited for not being an official emergency vehicle.

Too many cop impersonators doing bad things out there these days for me to put any accessory lighting on the vehicles other than exactly what toes the line for roadside safety, and then only when needed.

The cheapest and most available place to get help with this sort of thing is a car stereo shop. They do this stuff all the time. Many will show you how to get through the firewall and where the accessory pre-wired stuff is if you're going to DIY the install, for a six pack of beer at closing time if you're nice. Or they'll take cash, and most won't charge all that much to do a very professional install.

I had a problem with an accessory that was hard wired into a stereo once (added an iPod interface to a pre-iPod world stereo via tapping into the data line going between the XM receiver and "stealing" one of the XM "channels"). Thing worked fine but every so often, like months apart, the little converter box would freak out and the stereo would display "XM Error" and it wouldn't work anymore until power was disconnected and reset to it. And being that it was installed behind the dash, this suuuuucked.

Guy at a car stereo shop has the bright idea of just installing a toggle switch out of the way under the dash to kill power to the converter box and turn it back on. Worked like a champ. He drilled a hole for the toggle in the metal crossbeam under the dash, wired up a pigtail, wired it into the circuit, and had it all done in about 15 minutes and because I had purchased other stuff from his shop before, he said "no charge". Went in on a slow weekday to ask, out of courtesy, of course.

Most wouldn't charge much to wire up a few lights.

Some are downright craftsmen. I wanted a Kenwood dual-DIN deck in an old Dodge truck. Almost dual-DIN opening in the dash but not quite. Oddball Chrysler standard and what-not. The guy carefully removed the bezel and cut it perfectly by hand with a Dremel tool just a smidge, and then installed the deck. Unless you look hard, you'd never know the cuts were even there.
Yea I've checked CO vehicle lighting laws. Red or blue even being mounted is illegal from what I can tell. Amber and white are legal on private property, which as security is where they'll be used. If they need to be used on a public street it's because I have a bigger problem and I'm not worried about vehicle lighting codes.

Also anyone know anything about soldering? I need to solder a couple of points together. I tried the first time and it didn't do anything. I did make sure to use electrical solder and not plumbing solder

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I'll draw up a diagram of what I want to do in the morning and upload a photo of it

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