help me design my new electrical system

obviously cost effective kept in mind. Basically I am making a brand new harness for my truck, all new wiring throughout.

wondering if this is the starting point I need:
RFRM Rear Fuse & Relay Module 2.8mm Dual Bus 40 fuses, 10 Relays

seems the ones for 28$ with 5 relays just aint enough relays.

Truck is IDI powered, manual transmission so no real electronics to manage.
What I am controlling:

On means works only with ignion on, OFF means works either ignition off or on.

1)ignition (12v to fuel shut off solenoid, and close circuit to be able to engage starter)
ON2) fuel pump (on only with ignition on)
OFF3)Driving lights
OFF4)aux lights
ON5)turn signals
ON6)trailer wiring
OFF7)liftgate arming switch, winch arm, line lock
ON8)wipers, blower fan
OFF9)horn, radio, gps, 12v outlets, power to gauges
ON10) starter
ON11) glow plug circuit

I like all individual circuits so if something fails I dont have to chase down other circuits thru a process of elimination).

Wondering for this do I need the 10 relays, or can I somehow wire it to use only 5 relays?(defeating my want for having individual circuits?)

I just re-wired my entire truck. Built a box in the engine bay that holds all of my relays and fuse block. Everything in there is nice and neat, and easy to navigate. I used these relays http://www.amazon.com/Genssi-Relay-Harness-Bosch-40AMP-HRNS/dp/B00CUKXODI and they seem to be working well. I cant say how they will hold up over time, but so far they seem pretty durable. I though about going with an all in one block like you have there, but its just too much of a pain to trace things out in there. The only things that I'm running on a 12v hot switch with the key are the fuel pump, IP and glow plug relay. Everything else is controlled in the cab through a switch located on the dash. Wipers are on the original switch. Its not all that hard, just time consuming. I'm a stickler for neatness though, especially in this since I'm an electrician to begin with. Good luck with it, it'll be worth it to have all new wiring in the truck.

Oh and label EVERYTHING. I used one roll of 500' of black wire for everything, so if you dont have it labeled when you walk away from it good luck figuring out easily. I used Romex sheathing around the end of the wires since I use the stuff everyday and have an unlimited amount.

can you post some pics of your setup? tidyness is number one for me with electrical. All my wires thru the firewall are going to be twist on bulkhead connectors.
Wipers will probably use original switch, but im using an 06 steering column and wheel, would be nice to use the stalk mounted switch.

I assume you used the stock fosebox? I dont want to mess with that, I want all fuses easily accessible under hood.
NVM just re read your message

Looks like a good starting point, mind you I"d consider a 10 and 5 or two 10's for complete circuits along with future room to grow.

I'm not one for ALL one colour of wire as seen in my six wheeler thread I'm re-wiring it.

I"d get 100' Rolls of 14 ga, in as at least 6 colours, some 10 and 12 gua as well.

Get two or three quality PAINT marker pens then you can take the 6 colours of wires and have 27 different wires. Wire Green with WHITE tracer or Green with black or Green with red...and so on.

This makes it simple to draw up a diagram and track trace wires if problems occurr.

Run the wires, and cut longer and leave room to crimp solder heat shrink.

Have fun with it and don't get worked up. Take your time, and check, recheck and then check again..before hooking up the MAIN power....

The military connectors are great idea and don't forget DIELECTRIC grease on connections or IDEAL's NOALOX contact stuff, mostly for aluminum but still works well for other applications. I'm a fan of dielectric as a minimum mind you.

Well just take time, and do it right... maybe draw it out first then run wires.

JM2CW

This is all I have for now. I found it easier to make a complete list, then break that down into smaller chunks to do. For instance, I ran a ground for everything I would need, then constant hots, then 12v switch hots, ect. Dont make fun of my setup lol, it orks perfectly. I needed something that would have all the room to fit the relays and circuits, and close up well. I a going to make a metal box, but this was just too easy.

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The item you linked is just a plastic housing... you'll easily be in over $200 for the individual connectors, seals, crimp tool, relays, and fuses. There ought to be a better off the shelf solution. You can easily use less than 5 relays...

Headlights and fuel pump are the only ones that really need to be driven by a relay, unless you have other high-amperage accessories. The primary purpose of a relay is to reduce the need for long runs of high gauge wire.

It's redundant to feed your turn signal switch with a 20 amp switched relay for a couple amp draw. You're adding in another point of (frequent) failure and doubling your wire runs.

I'd highly recommend a marine fuse block and a couple of relays, just where needed.

im going to have to buy the connectors seals crimps and tool anyway to make the wiring systme the way i want it, removable weatherpack connectors at all points.
but that was my original plan before I found that thing.


So say for the turn signal switch, you just run power to fuse, and from fuse it goes power to the switch, and switch is grounded ya?

i would think all runing lamps on one relay (i got 100W hi beams), and aux lights (compined 600 watts of aux lighting) on another relay.
Carrier lift pump which only pulls 1.5 amps. So no relay even really needed?

I also assume i need a relay that trigers the bussed circuits that i outlined should be on only whne ignition is on?

For turn signals, feed switch with the respective fuse and no relay, then use switch to trigger a pair of relays for the rear brake/turn signals. Truck brake/turn lamps alone are no big deal as far as load goes, but hook up to a well-lit trailer with lots of non-LED lighting and you'll be in for some fun quick. Turn signal switch aside, remember that all rear brake/turn signals light up when you step on the brakes, and the BOO switch on the pedal is fed via a single 14-gauge wire and has to handle all that load - relays downstream from the BOO switch take care of that quite nicely.

Check out del city for parts & wire - they have a good selection of stuff and are decently priced.

LCAM, going to disagree a bit - I wouldn't try to use relays for brake/turn as it's one more thing to go wrong and unneeded complexity IHMO. How many brake lights are you thinking of having? Everything I've got is 2, even if you use the semi setup with 2-3 on each side it's still not that much current. Figure each bulb is ~2A, that's 8 at most, or ~16A. 14 ga wire is rated for 20A. (NEC rating, downrated to 15A for household GP use for factor of safety, insulation, etc) That being said, the voltage drop over that distance would be significant, so I'd probably use a bigger wire on the trailer, or LED lights, or just plain fewer brake lights. I doubt the switch or turn signal relay is up to that current either.

Brake lights are important enough that you want to minimize failure points. I'd even be willing to bet that it's somewhere in the NSTB standards that brake lights are direct wired as much as possible. Also worth noting that most general service relays are likely not designed for rapid on off switching like you'd see as a signal relay.

I would try to stay somewhat near the original wiring configuration as far as circuits and powering. It's done that way for a decent reason. Relays for headlights, trailer power, trailer running lights, and any high power auxiliaries you have (electric windows for ex) - no need to go too overboard.

Not in my Ford but I put a wiring center under the passenger seat. Just headlights on it at the moment but soon more...

As far as having everything on indvidual circuits, you can still do that with just a couple of relays. All the circuits go back to the battery or several common points at the ignition switch. What makes them individual is the fuse you use. So you can use a large fuse to feed the relay, and then after the relay use many smaller fuses to branch out to the different circuits. That way if you have a problem in one circuit, it will blow that one small fuse if it's sized right and leave the other circuits running.

The only advantage I see with using a bunch of relays is your wiring method. Of course you need a relay for a high current device, but if you use relays for other things and they are all out under the hood, you can wire them so all your control switches ground out to make the relay activate. So most of your switches will have a single wire running though the firewall to the switch, and the other side of the switch will go to a good ground under the dash. This cuts down on some of the wiring under the dash. A lot of the foreign vehicles are wired like this and Ford uses it now on their newer trucks to control the body modules.

I'd highly recommend planning it out by the draw of each circuit. Like others have said, you can minimize your need for failure prone relays.

For your light switch example... battery to fuseblock (likely one high gauge wire), fuse to switch, switch output to lightbulb, to common ground. An unfused terminal bus would work great for all grounds. I'm not a fan of chassis grounds in weather exposed areas. Rust and corrosion can goober it up.

jaluhn83 said:

LCAM, going to disagree a bit - I wouldn't try to use relays for brake/turn as it's one more thing to go wrong and unneeded complexity IHMO. How many brake lights are you thinking of having? Everything I've got is 2, even if you use the semi setup with 2-3 on each side it's still not that much current. Figure each bulb is ~2A, that's 8 at most, or ~16A. 14 ga wire is rated for 20A. (NEC rating, downrated to 15A for household GP use for factor of safety, insulation, etc) That being said, the voltage drop over that distance would be significant, so I'd probably use a bigger wire on the trailer, or LED lights, or just plain fewer brake lights. I doubt the switch or turn signal relay is up to that current either.

Brake lights are important enough that you want to minimize failure points. I'd even be willing to bet that it's somewhere in the NSTB standards that brake lights are direct wired as much as possible. Also worth noting that most general service relays are likely not designed for rapid on off switching like you'd see as a signal relay.

Click to expand...

Depending on the traveling configuration I can be up to 10 brake/turn lamps. With 3157 bulbs that's a bit over 20amps draw, after standing on the brakes for a while (traffic jam) I've actually felt the BOO switch get noticeably warm. Turn signal switch and flasher are also known failure points, which the individual relays eliminate. Failing relays is not high on my concerns list, as I have a pair of indicator lights wired after the relays and in parallel with the brake/turn lamps, much like how the factory turn signal indicator lights on the dash are connected to the front turn signals - if a relay fails I'll know right away, from there it's a quick job to pull over and swap it. Heck I know people who'd been driving around with dead BOO switches for what seems like forever and only realizing there is a problem after being pulled over by a LEO, my setup adds at least one layer of protection against that situation. Also not sure on the rapid on-off switching rating of the relays, I also thought about it but it's been years now and thousands of miles and I'm yet to replace a relay... Idk, to each their own, my setup works good for me

i am with LCAM abotu relauys being stout. I never considrred a relay to be a failure prone item. Those things just magically work all the time..for brakes, i might consider a solid state relay.