Centech & RJM harness questions

[Gunnibronco]

I've completely unwrapped & disassembled a perfectly good Centech harness.

I have a few questions, as I customize it for my set up, and try to remove as much extra wiring that I can.

First question is about adding headlight relays to the harness. Should I run new, heavier wire to the headlights or can I just tap into the harness & feed the headlights through the Centech wiring. I'm assuming the Centech wire is adequate. And just adding the relays will help my headlights.

I'm also developing a list/ball of wire that I figure I can pull out of the harness completely. I'll add that list later, to make sure I'm not pulling out something vital.

Thanks

[Gunnibronco]

Also, can I find the alternator trigger wire inside the cab on an RJM EFI harness?

I want to run an alternator light and would rather pull the wires from under the dash than run them from the engine compartment back into the cab and back to the engine compartment.

[Viperwolf1]

Headlight relays are best done under the hood. That's where you will tap into the high current and you can use the existing headlight wires (only need one side only) to trip the relays.

RJM should have the green alternator wire you need. The other end of it goes to one of the relays.

[Gunnibronco]

Thanks,

What gauge wire should run from the relay to the headlights? I have something you posted that says it needs a 20 amp fuse to the relays. So a 12g feed to the relay should be ok?

I am using the green wire in the RJM harness for the alternator. I just couldn't locate it once inside the cab. I'll keep looking & check out the relay pack.

[Viperwolf1]

12g is fine.

[Gunnibronco]

Thanks, things are coming along. I've pulled A BUNCH of unnecessary wire from this harness.

Since I'm using a 3G alternator & no amp meter, I have no real use for the heavy yellow wire that went to the "Batt" terminal on the stock alternator. Can I remove it from the back of the Centech fuse panel & use it to feed my extra fuse panel? The heavy red wire will feed the panel from the + terminal on the battery. Right?

[Gunnibronco]

What size fuse should I use to run the whole truck.

I want to use a Mega fuse holder I have to run the whole truck (except winch).

I'd run the Centech harness, EFI, headlight harness, & a 5 fuse aux panel (cb, and future stuff) fed by a 10g wire.

Thanks

[Digger]

First question is about adding headlight relays to the harness. Should I run new, heavier wire to the headlights or can I just tap into the harness & feed the headlights through the Centech wiring. I'm assuming the Centech wire is adequate. And just adding the relays will help my headlights.

I did the same thing you are doing. The Centech harness handles the current well and doesn't really require relays on the headlights. If you want to do that, run a separate heavy gauge wire to feed the relays. Alternatively you could ditch the halogen bulbs and go LED!

Since I'm using a 3G alternator & no amp meter, I have no real use for the heavy yellow wire that went to the "Batt" terminal on the stock alternator. Can I remove it from the back of the Centech fuse panel & use it to feed my extra fuse panel? The heavy red wire will feed the panel from the + terminal on the battery. Right?

You could. I pulled that one out because of the 3G alternator.

What size fuse should I use to run the whole truck.
I want to use a Mega fuse holder I have to run the whole truck (except winch).
I'd run the Centech harness, EFI, headlight harness, & a 5 fuse aux panel (cb, and future stuff) fed by a 10g wire.

How are you planning to power the EFI, headlight harness, etc? I fused the Centech fuse panel at 60amps, much higher than an 80 amp fuse and you risk melting sheet metal without blowing the fuse. (think about welding amperages) I used a Ford power distribution block to spread power to the heavy loads like EFI, ignition, engine fan, light bar, etc. The distro block can be fused at 100-150amps.

[Gunnibronco]

Thanks for the suggestions.

I've already started the headlight wiring as you and Viper suggested. Using the Centech harness as the signal wire to the relay & 12g for the headlight power.

Real good point about keeping the fused amps lower. I hadn't thought of that.

I'm trying to keep wiring minimal under the hood, and I don't want a bunch of in-line fuses hanging off the battery. I don't have a good under hood distribution block or a good place to put one. I have 2 Mega fuse holders and I'd like to use them under the hood.

My question now is about wire/fuse sizing. If I followed the 'max fuse charts' I find on-line, the Centech harness red wire is 10g, and would use a 30a fuse. The EFI harness is 12g and would use a 20a fuse. I have a bunch of 8g wire here, that would use a 50a fuse. I'm wondering why you chose such a high amp fuse for your Centech?

I'm thinking using 2x 50 amp fuses & run 8g through the firewall to behind the dash (about 2-3' of wire, max since my battery is recessed in the cowl now).

1x 50a fuse to feed the Centech harness (10g/30a) and headlight harness (12g/20a)

1x 50a fuse to feed EFI harness (12g/20a) and aux fuse panel (wire/fuses tbd)

Thanks again for all the help guys. I seem to be treading more water with this wiring than I thought I would. Finally found some 1/4" female terminals that snap into the relay bases I bought. Now I can get back to wiring.

[Digger]

My question now is about wire/fuse sizing. If I followed the 'max fuse charts' I find on-line, the Centech harness red wire is 10g, and would use a 30a fuse. The EFI harness is 12g and would use a 20a fuse. I have a bunch of 8g wire here, that would use a 50a fuse. I'm wondering why you chose such a high amp fuse for your Centech?

The distribution block I use came from my Ranger pickup. It used the same 60amp fuse feeding a 10ga wire to power the interior fuse panel.

Those wire ratings are a continuous rating. I'm guessing the OEMs fudge the numbers a bit and use a larger fuse to cover surges in the system. A quick surge could take down the system if the fuse was set right at the continuous rating. On the other hand, if the wire was operating above its continuous rating, it would eventually melt the insulation and short out, blowing a much larger fuse.

[Gunnibronco]

Thanks, its good to know how OEM does it in the real world. I think I'll wire it with 2 Mega Fuses & 8g. I'll probably start with 60a on each.

[Gunnibronco]

Getting into the engine compartment, I don't think I have a place for the following wires:

"COIL +","IGN PWR", & "START" all come from one 3 wire weatherpack. I have another "START" wire that I think should go to the "S" terminal on the starter relay.

Also "REG S" seems like it went to the old stock regulator maybe. Since I'm running 3G I don't think I need it.

[Gunnibronco]

Also, off the "REG S" wire there are 3 wires labeled "DIST MOD", "CHOKE", & "IDLE SOL". These wires seem to have no home either.

[Gunnibronco]

Obligatory Centech/wiper switch question.

I'm trying to splice the Centech harness to my Bronco switch pigtail & intermittent wiper switch. Their instructions are about as clear as mud.

My switch pig tail has the following wires:

Black
Black
Blue
White
Orange/white stripe
Green/black stripe
Red

The Centech harness has:
Black-park switch
Red- Park power
White- Low
Blue- Hi
?I forget- Washer pump

Thanks

[Digger]

Getting into the engine compartment, I don't think I have a place for the following wires:

"COIL +","IGN PWR", & "START" all come from one 3 wire weatherpack. I have another "START" wire that I think should go to the "S" terminal on the starter relay.

Also "REG S" seems like it went to the old stock regulator maybe. Since I'm running 3G I don't think I need it.

Coil +, IGN PWR both come from the main IGN SYS fuse. If you don't have a place for them, ignore them. Same with the extra START wire. It is powered the same as the other START. If you don't need it, tuck it away or remove it. Here are notes I took on the fuse block circuits hoping to piece together a wiring diagram after finishing the truck.



The Centech fuse panel has three main circuits,
(1) the stuff powered from the battery and always hot
(2) the stuff powered by the ignition feed from the main switch. These circuits are hot any time the key is ON or in start position
(3) the stuff powered by the ACC feed from the main switch. These circuits are hot when the key is ON or in ACC, but not HOT during START

Unfortunately the list doesn't cover everything because wires change colors and labels at various points in the runs, but maybe you can use the list to probe out stuff and remove what you don't need. For the most part, stuff behind the dash is covered by the list, but stuff in the engine compartments tends to change labels or a branch grows out of another circuit.

[Gunnibronco]

Yes, it's a tangled mess. I'm surprised how much excess wire I've pulled out. It's pretty bare bones now. I backtracked all the wires I don't need to 2 fuses: IGN SYS & ALT/EMM. From what I can tell, I don't need them at all, so I freed up 2 circuits with 12v key in 'Run' or 'Start'. I used the IGN SYS circuit to turn on the EFI (orange wire on RJM) & supply 12v to the winch & air compressor switches. I still have not used anything off the ALT/EMM wire. I need to hook up my CB, just can't decide if I want it to be switched or hot all the time.

Thanks for the help.

[Viperwolf1]

Even centech's own description of the wires adds to the confusion. I sure wish someone would make a diagram for it. I get a lot of questions on the centech wires but the different color scheme and poor instructions make it nearly impossible. I wish I was more helpful with this.

centech white=bronco white-orange
centech blue=bronco blue
centech red =bronco red
centech black=bronco black-white

Hey, those make sense.

Match those colors to the terminals on this diagram for a '70s wiper delay. An '80s delay will need one of the washer wires moved (unless already done) as I recall.

c-301.JPG

[Gunnibronco]

Thanks! I'll check it all out tomorrow.

[Gunnibronco]

Thanks for the pic.

My old Bronco switch pigtail wires were mostly the same, except circuit 950 is Black, and 58 is White.

Here is what I did, sorry no graphic design skills here.

Bronco Wiper Switch Pigtail ----> Centech Harness
950 Bk & 763 O/W---->O "Wiper Switch Pwr"
951 Gr/Bk---->Gr "Wash"
56 Bl---->Bl "High Speed"
28 Bk---->Bk "Park"
58 W---->W "Low Speed"
63 R---->R "Return"

I think this makes sense. Hopefully I don't let the magic smoke out of anything when I power it up. It will be a minor miracle if everything works, after all the hacking I've done. Knock on wood.

[Viperwolf1]

Looks ok to me.

[Gunnibronco]

I was just reading someone's post on FB regarding Centech & wiper motor wiring. I tried to answer his question, and had to go look at my truck to verify. I'm now wondering if I wired my motor correctly. This is what I did, please tell me if I have this right. He thought the red & blacks should be reversed from what I did.

Centech color/description-----> Motor wire color/Centech's description
White/low speed ----> White/low speed
Blue/high speed ---->Blue/high speed
Red/park power ---->Red/park
Black/park switch ---->Black/motor stop