“Dieting” the main Harness/Fuse Panel

[rhk118]

Hi All, just looking for any tips or suggestions on dieting the main harness and fusebox as I’m starting to wire my car. My setup is a 347 with Terminator X for ECU, MSD 6EFI Ignition and a dual sense distributor. The Terminator X will supply the trigger for the fuel pump as well as the fan relays. Having said that similar to the Coyote setups there is the entire wiring of the engine management system, then the wiring of the standard systems of the car with the RF harness.

I’m looking at the fusebox specifically to see what I can use to power other things, since the engine management system takes over some of these.

With my setup, I will use the Terminator X to activate the Fan relay in the fusebox - looks like the “green” temp sensor wire can be replaced with the Fan activation ‘ground’ the Terminator X uses to activate the relay. This would be a ground activation of that relay.

I will use the Terminator X fuel pump power line and replace the “orange” wire in the fusebox fuel pump relay. This will be a 12v switch for the relay.

Looking at the other things in the fusebox - on the ignition side looks like the “EFI or Coil” and “Choke” are open to be used for other things. My digital guard dog will supply ignition power to the 12v switches for the Terminator X and the MSD Ignition box, leaving these 2 fuse slots available to other electronics that will need a fuse…seem accurate?

The other area for opportunity appears to be the “Radio Memory” (which also supplies speedo memory) might be an extra wire I can use to power something, although is continuous 12V.

Finally is the radio power (runs with the gauge power) appears there is the ability to hook something else up on accessory power that doesn’t draw a ton.

Does this all seem reasonable? Specifically taking over the Ignition slots for Choke and EFI/Coil?

Any other things that can just get pulled out of the RF harness? (I guess anything I mentioned above that I don’t use can go).

Appreciate any and all tips

[burchfieldb]

I ended up ditching the fuse box and putting in a GEP PDM for my fuses and relays. Some of my wires on the fuse box were no crimped very well and were starting to come loose.

https://www.customconnectorkits.com/products/pdm-u3ac1

[PNWTim]

Hello - since I am neck deep in this, I can tell you what I have done. Running a Coyote, but you're right, somewhat the same guardrails as you have. I am using the electric choke to power my Dakota Digital Cruise Control. I am using the 30 Amp fan circuit to power my cigarette lighter/DC port. I plan to use the radio circuit to power my MagSafe charger/voltage Converter.

I personally stripped out the entire sensor gauge harness as I am running Speedhut gauges and don't need any of those. I removed a couple of the larger hot wires (alternator feed, starter feed) as I am going direct with those and they are redundant in the harness. You can remove the blue fan and green fan temp (I think that's what it says) if you are managing your fan operation through the Terminator X, as indicated.

I basically went through the RF harness, made sure I have the wires and circuits I need and deleted everything else. Double check your AC instructions as I believe one of those green fan temp sensor wires is used to power something, I just can't recall.

[Papa]

The two Fan Thermo Control (green) wires are the ground for the Ron Francis fan circuit relay. You can use the Terminator fan control (-) to run your fan by connecting to either of the RF green Fan Thermo Control wires.

[rhk118]

I ended up ditching the fuse box and putting in a GEP PDM for my fuses and relays. Some of my wires on the fuse box were no crimped very well and were starting to come loose.

https://www.customconnectorkits.com/products/pdm-u3ac1

I had that thought as I was going through things today…while the wiring harness is a nice “crutch” for someone who has never done this before (me) I feel like about 1/2 if not more of the main harness can go and I’m removing a lot of it.


Hello - since I am neck deep in this, I can tell you what I have done. Running a Coyote, but you're right, somewhat the same guardrails as you have. I am using the electric choke to power my Dakota Digital Cruise Control. I am using the 30 Amp fan circuit to power my cigarette lighter/DC port. I plan to use the radio circuit to power my MagSafe charger/voltage Converter.

I personally stripped out the entire sensor gauge harness as I am running Speedhut gauges and don't need any of those. I removed a couple of the larger hot wires (alternator feed, starter feed) as I am going direct with those and they are redundant in the harness. You can remove the blue fan and green fan temp (I think that's what it says) if you are managing your fan operation through the Terminator X, as indicated.

I basically went through the RF harness, made sure I have the wires and circuits I need and deleted everything else. Double check your AC instructions as I believe one of those green fan temp sensor wires is used to power something, I just can't recall.

Very helpful Tim and you’ve confirmed a lot of what I was thinking about the harness and getting a lot of those wires out of there (especially the alternator/solenoid wires). Like your addition of a MagSafe adapter, seems more definitive for the phone than a USB-C I was planning, will have to think about where to put that.


The two Fan Thermo Control (green) wires are the ground for the Ron Francis fan circuit relay. You can use the Terminator fan control (-) to run your fan by connecting to either of the RF green Fan Thermo Control wires.

Thanks Papa, figured it was ground and appreciate you confirming that for me!

[rhk118]

Just looked at the AC instructions and yes those green wires are used….the relay ground can be tapped into either of the green wires, but they should stay connected to the fan relay….just so I’m not confused that relay marked Fan in the fusebox is the main cooling (radiator) fan relay correct, which is how I’m interpreting it!

[PNWTim]

Just looked at the AC instructions and yes those green wires are used….the relay ground can be tapped into either of the green wires, but they should stay connected to the fan relay….just so I’m not confused that relay marked Fan in the fusebox is the main cooling (radiator) fan relay correct, which is how I’m interpreting it!

Yes, that is correct. I need to look at the schematic again but I think one of those green thermo wires ties into the trinary switch to tell the fan to turn on when the AC is engaged. If so, I may need to revisit my fan wiring as I was planning on using the Coyote to manage the fan with no input from the RF harness. I don't have the blue wire connected to my fan wiring so the green wires won't do anything at the trinary i.e. they can't tell the fan to turn on when the AC compressor is engaged because they aren't part of the fan power circuit any longer.

[PMD24]

I'm starting the same exercise. Are you planning to cut wires and seal the ends or remove them by depinning? I had originally planned depinning, but with all the different types of connectors for the RF and EFI harnesses, I haven't been able to determine brand for most to go looking for plugs to seal the depinned slots in the connectors.

Thanks,

Pat

[edwardb]

I haven't done a Terminator X. But several Coyote builds and sounds like some similarities. Some responses FWIW:


"50% of the RF wires can be dieted." Hyperbole, right? Yes there are opportunities. But not that many.
Removing the convolute makes removing unneeded wires easier. Plus for adding new ones. Also makes the overall harness more flexible and manageable in my experience. But I would caution not for everyone. Capping unused wires without removing works too. (1) If there is more than one in the same place, offset the length so there's no chance they can touch and short. (2) Put a piece of shrink sleeve over the end, Ideally the type with adhesive inside.
When breaking into the fuel pump relay, you still want the relay to be active for the ground path. That way the standard RF inertia switch will still work. It breaks the relay ground and continuity to the pump is broken. Assuming your setup doesn't have its own inertia switch.
If you're installing A/C, you need the RF fan relay to still be in the circuit for the trinary switch. So the cooling fan has two sources of power. One from the EFI system Terminator X in this case. Coyote is the same. And also from the RF panel when the trinary switch closes due to the A/C running and whatever pressure it's monitoring. Triggered by the wires that ground the cooling fan relay. I've done a couple builds this way and it works fine.

[rhk118]

I haven't done a Terminator X. But several Coyote builds and sounds like some similarities. Some responses FWIW:


"50% of the RF wires can be dieted." Hyperbole, right? Yes there are opportunities. But not that many.
Removing the convolute makes removing unneeded wires easier. Plus for adding new ones. Also makes the overall harness more flexible and manageable in my experience. But I would caution not for everyone. Capping unused wires without removing works too. (1) If there is more than one in the same place, offset the length so there's no chance they can touch and short. (2) Put a piece of shrink sleeve over the end, Ideally the type with adhesive inside.
When breaking into the fuel pump relay, you still want the relay to be active for the ground path. That way the standard RF inertia switch will still work. It breaks the relay ground and continuity to the pump is broken. Assuming your setup doesn't have its own inertia switch.
If you're installing A/C, you need the RF fan relay to still be in the circuit for the trinary switch. So the cooling fan has two sources of power. One from the EFI system Terminator X in this case. Coyote is the same. And also from the RF panel when the trinary switch closes due to the A/C running and whatever pressure it's monitoring. Triggered by the wires that ground the cooling fan relay. I've done a couple builds this way and it works fine.


- Yes total Hyperbole on the 50% Paul! Although that really big wire for the Alternator can go in mine and maybe I'll be 50% by weight with that one gone! :rolleyes: Although I am surprised how many wires I can either repurpose or remove
- PMD24 - Per above I am going to cut and cap the wires and at different lengths like Paul suggests. I can de-pin the connectors but I don't have exact replacement pins for the FFR adapters in case I bend one or snap it, so will seal the ends with a cap and adhesive shrink tubing
- PNWTim and thanks Paul - In the meantime I read the AC instructions as need to figure how I will route that wiring and did see that the fan is activated when the AC is activated. Thankfully it is also a ground switch to the relay like the Terminator X (and I assume Coyote) so should be able to splice two of those to the grounds of the fan relay. I've also see where some folks also put in a grounded switch to manually turn on the fan...maybe would be useful for a track day to manage temps, but with the terminator X you have control over the temp at which it triggers the fan on and off. Just a thought if you want that level of control over your fan.
- Fuel Relay - thanks again Paul - This is something the FFR manual also specifically mentions - Cut the orange (ignition) wire going into the relay and splice to the fuel pump power wire in the Terminator X (Or Coyote harness I presume) and the Terminator X will then supply 12V power turn on of that relay, but the grounded side will still use the inertia switch.

PNWTim - I also have Speedhut gauges...where did you source your temp / oil pressure information from for the gauges? Are these coming from the Coyote Harness in your case? I can diet out quite a bit of the harness for the gauges in my case but likely will need to leave those 2.

Once I've got it down I'm going to document everything on the Terminator X side of things to help others in the future...appreciate you all chiming in!

[PNWTim]

"PNWTim - I also have Speedhut gauges...where did you source your temp / oil pressure information from for the gauges? Are these coming from the Coyote Harness in your case? I can diet out quite a bit of the harness for the gauges in my case but likely will need to leave those 2."


I followed the F5 Coyote instructions and used the sending units that came with gauges. I don't think the Coyote PCM will provide this info. If you look in my build thread, post #300 and #303, I specifically called out the arrangement I used as they would only go together one way (at least for me). I also just posted a pic of the harness I made with those two Speedhut sending unit cables along with my Alternator charging wire since they all connect within inches of each other.

I am guessing in your case you will use the Speedhut sending units with adapters where the 347 picks up those data points - water neck or on the manifold for water temp and oil pressure down on the block. It's important to use their sending units as they are specific to the gauge.

[Smith is Retired]

Cannot offer much help but this thread does bring a flashback memory (nightmare) from when I built my Type 65 in '03. I sourced complete wiring harnesses from a Mustang donor car. I then sat on a small chair with a wiring diagram and a magnifying glass, cutting out all superfluous circuits. The amount of wire (and the weight) that went into the recycling bin was astonishing. Entire job took almost two weeks.

[rhk118]

Cannot offer much help but this thread does bring a flashback memory (nightmare) from when I built my Type 65 in '03. I sourced complete wiring harnesses from a Mustang donor car. I then sat on a small chair with a wiring diagram and a magnifying glass, cutting out all superfluous circuits. The amount of wire (and the weight) that went into the recycling bin was astonishing. Entire job took almost two weeks.

It is definitely tedious! Lots of little details and I have plenty of notes because my brain holds onto about 3 details for about 3 hours when it comes to this….I’d rather put the time in now and do it right once….remember that game show in the 80’s Press your luck? Well I’m hoping for no Whammies!

[PMD24]

It really does take a lot of time. Close to wrapping up the dash harness and gauges. Will be doing the Holley harness next. Lots there that isn't used.

The Speedhut sensing wires are really long and de-pinning the connector looks a little challenging given the extremely small size. Has anyone cut those wires and spliced them shorter? I'd probably solder. The smallest butt connector I have is for 22ga. Wires seem to be smaller than that.

Thanks,

Pat

[rhk118]

It really does take a lot of time. Close to wrapping up the dash harness and gauges. Will be doing the Holley harness next. Lots there that isn't used.

The Speedhut sensing wires are really long and de-pinning the connector looks a little challenging given the extremely small size. Has anyone cut those wires and spliced them shorter? I'd probably solder. The smallest butt connector I have is for 22ga. Wires seem to be smaller than that.

Thanks,

Pat

Pat - I’d be interested in hearing what you take out of the Holley harness. That thing is HUGE, but extremely inclusive with all the sensor data that thing collects. I’m reluctant to tear into mine as Holley was quite clear that you can’t shorten anything as it may throw off sensor data (well some things can be shortened, but others cannot). That’s at least for the Terminator X, maybe the Sniper is different if thats what you are using. But appreciate your thoughts if you do tear into that anaconda of a harness!

[rhk118]

Just to tie this thread up regarding Dieting the main FFR harness, here’s what I removed:

IGNITION/START SWITCH CONNECTORS:
1. Completely removed the Brown (ALTERNATOR IGN) and large red alternator (ALTERNATOR FEED) wires, which includes the Solenoid wire which is the other 1/2 of the large alternator wire
2. The small blue “EFI CRANK PWR”, Left the other, slight larger, one as that goes to the clutch safety switch for starting. I will tie my starter wire (purple) coming from the digital guard dawg into this so that the clutch needs to be in for the starter to crank. This part seems different than how the Coyote’s work, so will leave the FFR blue wiring/clutch safety switch intact so I don’t crank while in gear.

HOT ROD COLUMN CONNECTOR
- Pulled all those wires out of there, where they tied into other connectors, I cut them, capped, and shrink tubed them but left enough length (2” or so) in case I’d ever need to tap into the wire for any reason or repurpose that position on the connector

SENDING UNITS/ELEC CHOKE CONNECTOR - **ONLY IF YOU HAVE SPEEDHUT GAUGES**
- Removed:
1. Oil temp (light blue) - capped this at the dash harness connector, completely removed the other side of this from the dash harness
2. Oil Pressure (gray) - capped this at the dash harness connector, completely removed the other side of this from the dash harness
3. Water Temp (dark blue) - capped this at the dash harness connector, completely removed the other side of this from the dash harness
4. PURP-COIL—>TACH (purple) - This wire is a free wire in the EFI/COIL bundle and removed this entirely in the main harness as well as from the dash harness as my Tach wire comes off of my Distributor (MSD) and will connect directly to the tach gauge

What I Kept:
1. All the 3 grounds for the sensor wires on the dash harness side of things that I removed in case I need them, probably won’t and will trim them out as needed when I install everything, but no need to diet them out for now
2. Fan Thermo Switch (Dark green) - going to tie the Terminator X fan control ground relay wire into this wire - that way the Terminator X will control my fan from its temperature sensor, and I can set the parameters for temps it turns on/off in the Terminator X (I think the FFR sensor is on at 185 F and off at 150 F)
3. Electric Choke Wire (Tan) - This runs back to the fusebox to a fused line - I will keep this one and use it to power something else that needs a fuse
4. ORG-EFI OR COIL - This wire is in the bundle of EFI/CHOKE free wires (not going to a connector) and kept this one as it also goes to the fusebox to a fused position fed by Ignition power - so will use this to power something else that needs a fuse

DASH HARNESS
- I have the Speedhut gauges that come with their own sending units, and an old enough set that mine came with all the jumpers and dimmer, for better or worse, will be wiring those up today.
- Because of this I was able to pull the sensor wires out of the harness since the Speedhut gauges come with their own sending units that plug right into the gauges EXCEPT:
- Fuel level - this will come from the fuel level sender in the RF harness
- Speed Sensor - My Speedhut gauge for speed is a VSS version—not the GPS version (you can send in your GPS version and they will convert it to a VSS version for the cost of shipping alone)—so I kept the Gray and Green Speedo wires for now which connect to my transmission computer that sends the speed and controls the reverse lockout on the T-56
- Obviously I’m keeping the Dash lights (white), Gauge power feed (Brown), and Speedo-Clock Mem (Red) wires so that simplifies things a bit, complicated by running the sensors out of the engine bay and to the respective gauges.
- Also as mentioned above there are about 4-5 ground wires in the dash harness that I will keep in there for now and trim back once its wired.

So out of the 90 or so connections coming out of the main harness I pulled 16 out, not including grounds which will get pared back as I install things. It is crazy how much smaller and more manageable things are now. I don’t find pulling all the coverings off of the harness get into it as complicated, as things are taped and zip-tied together underneath, so it isn’t like its all going to fall apart into a bundle of wires, you can selectively take things apart, re-route as needed, then re-wrap….the wires everywhere problem happens when you go to install it all haha :rolleyes:

And it goes without saying, thank you all for your help with this!

[PMD24]

Pat - I’d be interested in hearing what you take out of the Holley harness. That thing is HUGE, but extremely inclusive with all the sensor data that thing collects. I’m reluctant to tear into mine as Holley was quite clear that you can’t shorten anything as it may throw off sensor data (well some things can be shortened, but others cannot). That’s at least for the Terminator X, maybe the Sniper is different if thats what you are using. But appreciate your thoughts if you do tear into that anaconda of a harness!

I looked at the Terminator X installation guide, and the harness is completely different than the Sniper2. But, for reference, here's where I'm headed with mine. If you call up the Holley S2 Installation guide and refer to the wiring diagram in the back, you'll be able to follow my logic and see what might apply to yours.
> I've cut the fuel pump relay trigger wire and spliced in the inertia switch. Jumpered the RF harness where it was previously.
> Kept blue wire that goes from the relay to the fuel pump
> Kept red and black primary EFI power that goes to the battery
> Keeping black with yellow stripe that goes to the 6 pin I/O sub-harness. This connects to the RF Harness fan thermo switch. I'll be removing every other wire to that subharness including the connectors. I'm not concerned about splicing. It isn't a sensing lead. Just a ground output to turn on the fan.
> Kept yellow to coil (-)
> Kept pink to RF harness tan electric choke
> Kept pink to relay
> kept red to relay
> 3 pin connector not used so removing that and the three wires that feed it
> white wire not used, removing it
> keeping the Can2 plug cable that comes out of the harness for now (4 wires). Using Can1 plug for setup. Not sure if I will use Can2 later so leaving for now. Probably removing later.

In summary, there are 16 wires coming out of the main Holley harness, with and additional 6 splitoffs for a total of 22 wires. I'm keeping 11. If I end up removing Can2, the final result will be 7 out of 22 kept.

Hope this is helpful in sorting out yours.

Pat

[rhk118]

Hope this is helpful in sorting out yours.

Pat

Sounds like a plan Pat! Surprisingly I was able to follow most of that…seems like I’m keeping mine pretty much intact and modifying/dieting my RF harness, and you’re doing a combo. My only issue is the fuel pump needs to be under 15A draw for the Terminator X harness and my fuel pump can peak at 25A per Aeromotive, but “usually” runs under 15A, just don’t want to risk it so running through the RF harness with a 30A fuse…