Which CENTECH wire is switched hot?

[jamesonfd]

Wiring a relay for the fuel pump; no battery yet, and I'm not good enough to figure it out cold. Does anyone know which wire off the ignition switch is switched hot and appropriate to trigger the relay for the pump? Much appreciated!

 

[dbevans2249]

Jamesonfd, look at the fuse panel. You will see it is devided into three sections. One is hot all the time. One is hot with the key on only (that is where you want to get power from). One is hot with the key in both the on and acc positions. You also need power when the key is in the start position. The starter side of the starter relay is a good place for that.
A 9v battery or a 6v lantern battery are great for testing circuits and wont fry the wires like a car battery. Two 6v lantern batteries will operate relays. I dont know if one will as I never tried it. I used two when I did my centech wiring and it was a big help.

 

[red hot71]

Under the hood passager side there a pink wire labeled opt.1,its shares a plug with a opt. ing. wire for I think a hei,anyway the pink one should switch your relay.

 

[DirtDonk]

Definitely. And if you're running a modern internally regulated alternator now, you will have at least one more wire over there as well. Should be Green if I remember, and will be labeled with some semi-appropriate wording.
If you're using a stock-type alternator though, don't tap into that one at all.

Paul

 

[crews44]

Paul,

IS this the one that says "reg"? (Im not being smartass) Im trying to tie my mustang harness into my centech harness.

 

[DirtDonk]

Yes. Should be Green (there is a Yellow one too) and would say "REG" but not sure what else. Maybe "REG +" or "REG + IGN" or some version of that, to let you know that it's not constant power.
But then, you can simply test for that aspect. If it's hot only with the key, that's the one.

I take it you're using an internally regulated alternator then? How powerful?
Reason I ask is that it's a good thing to run a more powerful alt usually. Just don't use the existing Centech Yellow wire for your charge wire.
If you're running a 70 amp or less alt, that wire is just fine. If you're at 95 or more (like most late-model Ford alts), then you need to bypass that one if you haven't already.

Paul

 

[jamesonfd]

Thanks, guys! got it, and much appreciated!

 

[jamesonfd]

I'm running (or will be) a 4G; 99 Explorer 5.0 with GT40P heads, EFI with Ryan's harness.

 

[crews44]

Paul,

(Total Hijack sorry OP), I am running the explorer serp but I have already switched to the 2/0 charge cables from JBG and have 175Amp mega fuse attached. I have RJM's alt connect but what do I hook that to? Is that to trigger the gage?

You said on the Centch that the yellow alt wire and red bat + ar ethe same wire on different ends correct? I havent dug into this yet but had harness laid out and went down through each wire trying to identify ones I know I have Q's on and these were some...

Thanks and be ready for lots of Q's and PM's!!!!!

Steve

 

[DirtDonk]

...(Total Hijack sorry OP), I am running the explorer serp but I have already switched to the 2/0 charge cables from JBG and have 175Amp mega fuse attached. I have RJM's alt connect but what do I hook that to? Is that to trigger the gage?

Hey Steve.
Do you have the RJM 3G or 4G adapter harness as well? Oops, you said you did I think.
If so, the basic way (ignoring the dash light for the moment) is as follows:

1. Run the 2/0 wire straight to the battery (or starter relay) as it sounds like you've done.

2. The small Yellow wire from the RJM connector to the output stud of the alternator (along with the main 2/0 charge wire). This is the sensing wire.

3. The Green w/red wire needs a 12v switched source. Your RJM's main engine harness should have a plug ready made for this, and gets it's power (along with the ECU I think) from the firewall connector on a stock harness, but from the passenger side trunk on the Centech. He sells an adapter/extension harness for aftermarket harnesses like the Centech, because his standard plug is right there behind the engine. But there should be a plug right there by the number one injector plug that attaches to the alternator harness.
For the Centech, that should be the Green wire marked "REG" there along the passenger fender. With the Centech though, there are at least 2, if not 3, wires right there with 12 volts on-with-the-key. You can use any of them.

4. Depending on which alternator adapter harness you have, there may be a White w/black pigtail with connector already on it. That's your Stator wire and is usually not used on an EB.

The proper way of completing the alternator circuit would be to add the dash indicator light into that circuit that turns the alternator on. There are diagrams showing how to do it here and in the shop manuals with diagrams of vehicles with a light instead of an ammeter.
The system will work without a light, but it's been argued that it's better for the alternator if that little extra resistance from the light bulb is in the circuit.
I don't know how that works, but it's just good practice to have a light anyway. Even if you have a volt gauge in addition to it.

You said on the Centch that the yellow alt wire and red bat + ar ethe same wire on different ends correct?

Correct. And you've just made the Yellow half unnecessary with your 2/0 charging cable. So you have options.
1. You can leave the Yellow wire attached to the alternator, even though it's not really doing anything.
2. You can cut it off and safely cover it so it never gets touched by anything (since it has constant battery voltage.
3. You can re-route it now, to power a large distribution terminal/stud for an easy place to hook up additional accessories later.

Up to you.

Paul

 

[plumbdoctor]

Paul, a little hijack, how hot should the 3g be while running? Mine seems to be wicked hot... is this normal?

 

[DirtDonk]

Might be. They get too hot to touch just during normal operation, but there is a point where the heat could be too much, or indicative of something wrong.
However, I wouldn't have any idea how to tell that merely by "touch" in this case.

I guess we'd have to take a running temp of a known-good system, so we'll have some numbers to compare to. Then, the way to verify yours is to get one of those infrared thermometers too, and compare yours to the numbers posted.

At the very least, just measure the voltage at the battery while the engine is running. As long as it's not much out of the range of 13.4 to 14.5 volts, you should be good to go.
If you're showing 15 or more, you're probably over-working your alternator. Hence the heat.

But unless you're seeing smoke, I wouldn't worry overly much about it until we have something to compare to.
And, if yours has been running on a low battery, perhaps it's just being worked hard temporarily.

Paul

 

[crews44]

Hey Steve.
Do you have the RJM 3G or 4G adapter harness as well? Oops, you said you did I think.
If so, the basic way (ignoring the dash light for the moment) is as follows:

1. Run the 2/0 wire straight to the battery (or starter relay) as it sounds like you've done.

2. The small Yellow wire from the RJM connector to the output stud of the alternator (along with the main 2/0 charge wire). This is the sensing wire.

3. The Green w/red wire needs a 12v switched source. Your RJM's main engine harness should have a plug ready made for this, and gets it's power (along with the ECU I think) from the firewall connector on a stock harness, but from the passenger side trunk on the Centech. He sells an adapter/extension harness for aftermarket harnesses like the Centech, because his standard plug is right there behind the engine. But there should be a plug right there by the number one injector plug that attaches to the alternator harness.
For the Centech, that should be the Green wire marked "REG" there along the passenger fender. With the Centech though, there are at least 2, if not 3, wires right there with 12 volts on-with-the-key. You can use any of them.

4. Depending on which alternator adapter harness you have, there may be a White w/black pigtail with connector already on it. That's your Stator wire and is usually not used on an EB.

The proper way of completing the alternator circuit would be to add the dash indicator light into that circuit that turns the alternator on. There are diagrams showing how to do it here and in the shop manuals with diagrams of vehicles with a light instead of an ammeter.
The system will work without a light, but it's been argued that it's better for the alternator if that little extra resistance from the light bulb is in the circuit.
I don't know how that works, but it's just good practice to have a light anyway. Even if you have a volt gauge in addition to it.




Correct. And you've just made the Yellow half unnecessary with your 2/0 charging cable. So you have options.
1. You can leave the Yellow wire attached to the alternator, even though it's not really doing anything.
2. You can cut it off and safely cover it so it never gets touched by anything (since it has constant battery voltage.
3. You can re-route it now, to power a large distribution terminal/stud for an easy place to hook up additional accessories later.

Up to you.

Paul

Paul,

Thanks for the input. I called Centech and they said to use the green "reg S' wire to attach to RJM's adapter I have for the 4g. So you were right on money there. I could have used and switched Hot in Run wire though as this is the exciter I believe.

On the Yellow Alt wire I could cut capped thoroughly and left in harness for now. I am going to be reworking a Mustang harness for use with my efi. So I am assuming I could use the yellow Alt wire to power my fuse block I am going to using before the Relays I am hooking up..Correct?

I think I have most of this wiring under control but may still have more questions down the line.....I will start my own thread though....thanks....


Steve

 

[DirtDonk]

Good idea. These questions have a way of spiraling quickly out of control!
And yes, you can use the old Yellow "ALT" wire from the Centech harness to power pretty much anything you want. It's a high-capacity circuit (10 gauge most likely) and is protected at the Red end (starter relay end) by either the supplied fusible link, or a Maxi-Fuse if you prefer. Personally, I like fuses better than links in this circuit, because they're easier to service out on the trail or open road.

Paul

 

[AZ69EB]

Another quick Centech tip:

You can also use the threaded lugs on the backside of the fuse block to add more circuits. One is hot all the time and one is hot ignition on only. This is where I wire my transfer pump too.

Just be conservative.