This is an easy project that will give you a number of additional fused circuits for your various 12V accessories. As I have it wired, a relay is activated by a key-switched accessory circuit on my factory fusebox; the relay switches on and voltage directly from the battery is sent to a small fuse panel mounted under the dash on the firewall.

When I put my setup together, I bought a relay and the rest of what I used was spare parts. It's held up fine, but below I've tweaked the setup for both better results and better appearance.

The parts you'll need to do this:

- A multimeter or voltmeter
- Pliers or a wirestripper/crimper tool
- One add-on fusebox; mine has six circuits rated for 30 amps each
- One Bosch-style 12V relay, rated for at least 30 amps
- A length of 8ga. wire to run from the battery to the relay
- A length of 8ga. wire to run from the relay to the new fusebox
- An inline Maxi fuse holder and fuse (I'd say 40 amps would be good) OR a 40-amp fusible link
- OPTIONAL: An inline standard ATM fuse holder (same size as what your truck uses) and a low-amp fuse, to protect the switching circuit, OR a low-amperage fusible link

- A length of wire (12 to 14ga. is good) to go from the key-switched circuit to the relay
- Another length of wire (12 to 14ga.) to go from the relay to a ground
- Spade connectors, male and female
- Eyelet connectors for connecting the 8ga. cable to the positive battery clamp, as well as for connecting the ground wire to ground with a screw, bolt, etc.
- An assortment of fuses (you want your accessories to get power, don't ya? lol)

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1. First, figure out where you want to mount your fusebox. I have mine under the dash near where the steering column goes through the firewall.

2. Mount the relay near where you mounted the fusebox. I used a small screw threaded into a hole in the top right corner of the factory fusebox to mount mine.

3. Decide where you want your key-switched power signal to come from. I used an unfused accessory terminal on my factory fusebox. Run a length of 12-14ga. wire from there to the 85 terminal (this is your SWITCHED POSITIVE 12V source).
OPTIONAL STEP:I didn't add an inline fuse for this wire on my setup, but if you choose, you could put a low-amp fuse or fusible link in line between the factory fuse box and the relay to protect this circuit, too.

4. Run another length of 12-14ga. wire from the 86 terminal to a good ground (this is your GROUND for the SWITCHED POSITIVE 12V). You've just finished wiring up the switching circuit for your new fusebox.

5. Take a short length of 8ga. wire, around 12 inches long, and crimp an eyelet connector onto one end. Connect this end to the positive battery clamp.

6. On the other end, use a butt connector (or solder) and add in the inline fuse holder or fusible link. If you use the fuse holder, you can choose to leave the fuse out for now, so you're not working with a live wire.
NOTE: I have my fuse holder mounted under the dash right near the relay, but I've learned it's better to have it as close to the battery as practical.

7. Add another butt connector (or solder) and run a length of 8ga. wire from the fuse holder to the new fusebox and relay.

8. Crimp a spade connector onto the end of the 8ga. wire that you just routed from the battery and fuse holder, and connect it to the 30 terminal. This is POSITIVE 12V FROM BATTERY.

6. Run a length of 8ga. wire from the 87 terminal to the add-on fusebox.
NOTE: There may be two 87 terminals on the relay. I used the outermost one, and left the center 87 (may be labeled 87a) terminal alone.

7. You've finished with wiring everything. Now it's time to test to make sure everything works.

8. Using your voltmeter/multimeter, check your battery voltage.

9. EXTRA STEP: If you have a multimeter, set it to ohms. Put one lead to the 86 terminal on the relay, and the other to a good ground. If you get continuity, you're good to go on to the next step. If you don't get continuity, check your ground connections between the relay and its ground.

10. Now we're checking for positive voltage. Go into the cab and put a fuse in one of the circuits on your new fusebox. Doesn't matter what amp rating, we're just checking for voltage.

11. Turn your key to ACC or RUN. Using your voltmeter/multimeter, put the POSITIVE lead to the terminal after the fuse you just put in (the side that's protected by the fuse), and put the NEGATIVE lead to a good ground. You should see the same positive voltage reading that you got when you checked your battery directly.

12. If everything checks out, you can continue on to wiring in your accessories. Make sure and fuse everything properly.



EDIT: I added some steps I accidentally left out (forgot about the fuse for the battery-to-relay wire...whoops) as well as some alternate part suggestions (thanks JimsRebel for the ideas about fusible links).


Below is a handy little wiring project I just finished earlier this week.

 

good info thanks

 

I was looking for a how-to thread on how to do this yesterday for some accent lights and whatnot. Thank god I found a good thread thanks to you!
It seems pretty easy too!

Thanks TheKirbyMan! (:

 

Awesome info. I really could have used the cigar lighter tip a few months back, but since I removed the ash tray to install my gauges I relocated my Cig lighter to the glovebox. Now I can safely leave things charging without worrying about someone stealing them. Most of the steps you used TKM are exactly what I did when I moved mine.

 

The above looks good, just some fine tuning:

I don't see the inline fuse being installed in the large power feed wire. I think you have it in the list(30 amp inline fuse) but forgot to talk about it being installed in the line. A fuse or circuit breaker will work, just make sure you install it as close to the battery + terminal as you can, so it protects most of the power feed wire in case something bad happens to this wire. The battery has a lot of power potential, and can turn that 8 gauge wire red hot in a second if it got shorted.

I also recommend this inline fuse or circuit breaker be larger than any one single fuse in your aux fuse box. It doesn't matter really, but it makes troubleshooting easier. For example, you listed a 30 amp fuse to protect the main power wire, and you used a 30 amp fuse for your cigarette lighter project. This is fine electrically, but if something happened to the cigarette lighter circuit, there really is no predicting which fuse would blow first. Since the 30 amp fuse at the battery is farther away, it probably would not blow first, but it's easier and more predictable if you make the main fuse a 40amp or larger(the 8 gauge is plenty big for that) and made the cigarette lighter fuse a 20 or 30 amp.

 

I would recommend changing the main power feed point for the new fusebox.

You are current using the battery side of the solenoid as the feed point for the new fusebox. If you use the battery as your power feed point, all current draws on the new fusebox will cause the amp meter to deflect to the charge side directly proportionately to amp draw going to the new fusebox.


If change the power feed point to the power output stud on your G1 alternator, the amp meter will still read correctly. This idea would work best if the extra loads are only added after the ALT is on line and the extra current draw is not that high, say under 30 amps. If the ALT was not online the current would feed through the existing fusible link and you could risk burning it out if your total amp loads were too high…high beam lights, fan plus the extra fusebox stuff.

A fusible link would work good to protect the new fusebox.
Jim

 

I had a feeling I forgot to mention something. I'll add it to my post, thanks for pointing it out.

All of that makes good sense. I updated my post accordingly. Also, now that you mention it, I'm starting to wonder if the wire I used from the battery to the relay is 10 gauge and not 8...doesn't matter much right now, I suppose, since my setup only sees small loads currently. When I upgrade everything later on, I'll use 8 gauge instead.


I have the 8ga. wire directly connected to the positive battery clamp. I thought it would have caused the ammeter to read lower....interesting, thank you for pointing this out!

Quote:

Originally Posted by JimsRebel

If change the power feed point to the power output stud on your G1 alternator, the amp meter will still read correctly. This idea would work best if the extra loads are only added after the ALT is on line and the extra current draw is not that high, say under 30 amps. If the ALT was not online the current would feed through the existing fusible link and you could risk burning it out if your total amp loads were too high…high beam lights, fan plus the extra fusebox stuff.

This idea makes good sense, but I'm worried that if I tie into the charging system this way, I'll get weird readings on my Autometer voltmeter (correct me if I'm wrong). I say this because I once had my Autometer voltmeter wired to the key-switched circuit on my factory fusebox, and any time I'd turn on the headlights, heater, or other accessory, the needle would vary pretty drastically. I figured this was due to voltage drop through the factory wiring, since it's pretty small gauge to begin with.

When I got my relay-switched fusebox set up, I was then getting voltage readings straight from the battery and the needle now reads smoothly and realistically. As I said, correct me if I'm wrong in saying this.

Quote:

Originally Posted by JimsRebel

A fusible link would work good to protect the new fusebox.
Jim

I like this idea, it would give a more factory appearance, plus it'd be more weatherproof. I may just replace the inline fuse I currently have with a higher amperage (40+) fusible link since I want to eventually upgrade my setup anyway. I may use one to protect the key-on switching circuit too; what's the lowest amperage fusible link that you know of?



Thanks for all the comments and ideas, everyone. Sorry about leaving out a few steps, hopefully now I've covered all the bases and no one will be calling me up asking for a fire extinguisher.

 

I follow Jim's theory on the ammeter, never really thought about it before. But in reality;

1. The factory ammeter hardly ever works in the first place. Maybe some of them work but I never had one that did much of anything.

2. In your case with a small aux fuse box, you can pick and choose where you want to put your aux load, but in the case of something big like my snowplow, I have no choice but hook it to the battery directly. No other place is going to supply the amount of power I need for a short period of time like the battery will. That goes for winches and anything else with a large load. Even some big amplifiers and large power inverters are going to have to be hooked directly to the battery.

 

My amp meter doesn’t really work that good, but there are some out there that do work as they should, here is a link with a good photo. When I installed the head light relays is when I realized I had bypassed the amp meter shunt. I have a G2 ALT and it doesn’t have a post for the power output to connect anything to, it has a snap in plug for the power output.

https://www.ford-trucks.com/forums/1...ml#post9577859

If the voltmeter is reading battery voltage at the battery it will give you the most stable readings as the battery act as a large capacitor to smooth out the voltage reading. But the voltage fluctuation can also provide you with useful information. If the voltage drops a little when you turn on the lights… well you know that the lights are actually on.
Jim

 

I'll be running accent lights all around the interior of the truck.

I'm also going to install a Mono Channel 1000watt RMS Amplifier for a 12" sub and a 4 channel 500-600watt Amp for the speakers.

How should I wire this?

Should I put each Amplifier on it's own separate line with it's own fuse? If so, What size fuse? Do I need a capacitor for the 1000W Mono Amplifier?

Then should I just do a small 20 amp fuse box for the accent lights?

What would you do?

Thank you so so so much!

~Andrew S.

 

Project for the weekend. Thanks for the great writeup!

 

You need to get the specs on the amps. By that I mean the power they require to run them at full output. You might be able to find this online if you haven't bought them yet. Then you can do some planning. If you find out the power requirements, post back.

Same with the lights. How many lights, and what is the wattage of each light?

 

This made me think. Perhaps I could get the best of both worlds by wiring my Autometer gauges (including the voltmeter) on a separate relay that gets power straight off the battery (as it's currently wired), then have another relay wired as I have it now, BUT it would get power from the terminal you mention on the alternator. That way I'd get smooth voltage readouts on my gauge, but the large loads I may eventually put on the fusebox would register correctly on the ammeter.

Agreed. Though this is just my way of thinking about it:

By having the voltmeter wired through my truck's factory electrical system's wiring, I'm able to see voltage drops occurring in the system that may affect factory-wired accessories and such, voltage drops that don't show up much if at all when measured at the battery directly. This wiring method could help me track down problems in the factory wiring.

However, it isn't a true representation of the condition of the battery itself; in fact, before I wired my voltmeter to the relay-switched fusebox, I was getting lower voltage readings on the Autometer voltmeter (about 13 to 13.2) than what I got with my digital multimeter at the battery terminals (13.8 to 13.9). Not much difference on the multimeter, but this is a pretty good difference on the Autometer gauge.

My ammeter actually works (surprised me too); the needle goes toward D just a little bit when I turn the lights on or another high-power accessory. So I still can know that my lights are actually on as you said.

When I start my truck, the needle moves toward C a fair bit indicating that the alternator is putting back what the starter took out, but the needle drops back to the center after a second or two.

I second what Franklin2 said, report back with more info on your amps and then we can help you from there.

As far as the lights, I would think a setup like what I wrote about here would work fine. I would consider pairing the lights in groups. Say you have under-dash lights, have those wired to where they're on a single fuse. Dome light or map lights, have them on another single fuse.

Just don't do what I've done in the past and rush yourself or throw stuff together. I'm eventually going to have to pull most of my custom wiring I've done over the years and redo it properly with heatshrink wrap, solder, etc. and have it all bundled nicely. I did pretty good with the switched fusebox setup, but other stuff, while safe, resembles a spaghetti sandwich of wires of the same color.

As you can imagine, it's interesting when I need to check why something isn't working. Sometimes I wonder if I should just flip a coin...lol

No problem! Let me know how it goes.

 

Thanks for the write-up, Kirby, I added it to the Sticky.

https://www.ford-trucks.com/forums/8...ml#post7434560

 

Awesome!! Always happy to oblige. So many people (including yourself) have shared so much knowledge with me, I'm more than happy to share what I've learned.