3G with Centech, Mustang EFI Harness

[bronccar]

I think I have most of this figured out but wanted to be sure before I start ordering. Questions in red.

• 4 ga AWG copper with 175 amp circuit breaker from Alt to Batt (or solenoid as pictured
• Ground to Alt chassis? What size wire?
• Rest as per Centech diagram
• I assume the mustang harness isn't directly involved in this
• How many feet of hot wire / ground wire needed roughly?

Centech diagram:

 

[DirtDonk]

• Ground to Alt chassis? What size wire?
  
  No set value for that, as most of the grounding happens between the case and the engine block. So make sure that your mounting points are clean and rust free, and that your engine block is well grounded.
  If all that applies, then a simple 10ga ground wire from the alternator to the body or battery is a nice little bit of extra insurance.
  
  
• I assume the mustang harness isn't directly involved in this
  
  Correct to a point. The ECM does not control charging like they do on many newer vehicles, but depending on your engine harness, the Green w/red wire might be integrated. It's that way with our EFI harness to make a cleaner install.
  Otherwise it's all about the chassis harness. No EFI stuff involved.
  
  
• How many feet of hot wire / ground wire needed roughly?
  No way to tell. Everybody runs their wires through different routes and convolutions. But at the very minimum you would need 18" or so if you just ran it straight from the alternator to the post on the starter relay.
  The ground would all depend on where you were grounding it.
  The last two I did I remember running a ground to one of the stud/bolts on the side of the intake manifold, where I also put the ground strap between the engine and the firewall. Might have been one of the bolts holding down the injector rail.
  I tend to route wires hither and yon to keep them tidy and tucked away. This usually ends up tripling the length of wire you could "get away with" on most installations

Good luck.

Paul

 

[bronccar]

Thanks Paul.

All of my mounting hardware is fresh painted - will 10 ga still be sufficient to the battery?

10-4. Harness is 93 mustang - not sure about that wire.

Gotcha.

Thanks!

 

[DirtDonk]

With a Mustang harness there might very well be a Green w/red wire (and even a Yellow one?) running along the manifold to the front of the engine. If you see one or two like that, check for 12v with the key in RUN.
That color combo is ONLY for the alternator exciter wire on older Fords. No idea if they have more of that color on newer cars, but back then the alternator was the only function for that color wire that I know of.
So check it out. If it's there you can use it for your alternator.
You'll still need the Yellow wire connected to a battery positive source. Ford runs it back closer to the battery (probably the starter relay again) like your diagram shows, but most people just use a shortened version connected directly to the large alternator output post and charge wire.
So look for a Yellow wire in that bundle too.

As far as the alternator case ground goes, I'm not sure. Maybe Viper or one of the others will know if it needs a full size ground cable (same size as the engine ground) if it's not able to connect to ground through it's case and bolts.
I'm thinking it only needs that same 10ga wire we talked about, but I'd hate for you to have to chase charging gremlins down because we had insufficiently sized wire. That would suck for such a simple fix.

Paul

 

[bronccar]

When you say "yellow wire connected to battery positive source" do you mean the yellow / white wire? (I.e. not another solid yellow wire)

As for the harness, if I have that wire:
1) it connects to the green / red from the alternator - correct?
2) whatever it does, doesn't affect the yellow / white wire's plan - right?

Thanks a bunch!!

 

[DirtDonk]

Yes, Yellow w/white. Sorry.
Early models like came stock on our EB's were solid Yellow. I forget they put the white stripe on the newer ones. We have a Yellow w/white on some EB's too, but it's for the AUX tank sending unit.

And correct on the two having different duties. They both go to the alternator, but they have two separate functions.
The Green w/red wire is simply 12v with the key in RUN to tell the alternator it's ok to "turn on" when the engine starts to spin it. If it was hot all the time it would drain the battery.

The Yellow is always hot and is the sensing wire to tell the alternator how much to put out in order to keep the system running and the battery charged.

The White w/black wire is the Stator wire and I'm not really 100% sure what it's function on the 3G is.
On earlier models with the external regulator it had more duties, but some 3G's work with it unplugged, and some work with it plugged in to the side terminal of the alternator.

Paul

 

[bronccar]

Thanks Paul - immensely helpful as always!

 

[DirtDonk]

Yes, but is it accurate?%);D

Thanks!

Paul

 

[bronccar]

Funny you say that bwahahaha

I talked to Brian (he re-worked my harness) and he said the exciter is not in my harness so just run outside of the harness

 

[DirtDonk]

Perfect. So you don't have to dig in looking for wires that don't exist. Just add your own.
The Green w/red wire should come from the key in RUN only (not in the ACC position) but with the Centech that's easy.
They have a Green wire marked something along the lines of "voltage regulator bat +" or similar. Should be over on the passenger side in the big bundle.
There are extra green wires (some are doubled up in a white plastic connector) that might be on in both RUN and ACC. So double check when the wires are powered and pick one that's only hot in RUN if you can.

The only reason to use a RUN only wire is so that you can listen to the radio for hours and not be drawing power (even though it's not a huge amount) from the alternator/regulator. It'll help you run the accessories for longer before you have to start the engine and re-charge.
Not sure it would hurt the regulator, but without the fan going to cool things in there, I suppose it could get hot over time if enough current was flowing through it.

Paul

 

[brianstrange]

When it comes to grounding, I suggest a ground from the - post on the battery to the front right engine stud, in a 4 awg or larger wire. Also, add an intermediate grounding point to the frame using that same 4 awg wire. Then, run a small 10 awg from the - batt post ti the inner fender area, and another from the rear engine block to firewall.

 

[bronccar]

Thanks guys.

So Brian:

4 AWG from batt to engine stud
4 AWG from engine to frame
10 AWG from batt to body (radiator support? no inners)
10 AWG?? from rear of block to firewall

So 4 AWG from ALT to Battery (-) ?