lost in wiring...

[stuchman1]

Friends,
We're working on installing gen 3 Coyote. Between the main manual, the wiring manual and the Coyote fitment manual, it's somewhat bewildering despite reading multiple other posts on similar topics. I'm missing something.

Two main questions:

- First, the Coyote manual talks about adding the 250A fuse to the wire at the back of the fuse box and then running wire from there to a battery cutoff or the starter battery cable. On our harness, we have a red wire at the back of the fuse box running into the harness. Is the manual referring to an old version of the harness where you connect starter to FPPDB directly through a wire you add and on the current harness, they already include a wire that runs through the harness to the starter? Pictures attached of our harness / fuse box as well as the manual with fuse in place. (I'll be honest that I've tried to solve this through continuity testing to no avail. I'm clearly missing something.)

With that in mind, to confirm, do we just add the fuse to that wire at the back of the fuse box and we do not run (another) wire from that fuse to the starter? (Part of my wanting to check is that the terminal on the existing wire doesn't fit on the post of the fuse, so I'll have to drill it out a bit.)

- Second, we have a four post / two pole battery cutoff switch from FF that comes with no instructions. I've read the posts regarding the merits of mounting on the positive vs ground sides and don't feel strongly. We're not racing so those restrictions don't apply. When in doubt copy EdwardB, and so with that in mind I've been looking his and others' posts describing wiring the FPPDB to keep power running to the PCM even when the switch is off, schematically depicted in the attached diagram nicely done by Facultyofmusic. But I'm having trouble translating that into how to actually make that happen in our car, meaning where do I place the switch within the current wiring on the car, and what wires go to what posts on the switch. My lack of clarity on point #1 above, specifically regarding how power is actually getting from battery / starter to FPPDB, has made figuring this out difficult.

Sorry for the noob questions - just trying to do this right.

Thanks!
Sascha

[edwardb]

Agree there are a lot of variables and easy to get confused between the various instructions. Hopefully this gets you in the ball park for both questions:

The existing red wire in the Coyote harness to the PDB -- leave it alone. You need to add a +12V battery cable from your power source to the 250 amp fuse and then a short length of the same cable to the PDB post. The PDB post will then have two connections.

Depending on your wiring scheme, the power source could be coming from your starter post as you mentioned if you have the battery power going there first. But if you're installing a master disconnect as you also asked about, you really want the battery power to go to the master disconnect first. Then a cable on the same post as the battery cable to the Coyote PDB through the mega fuse. That will give the Coyote always on power as the Ford instructions describe.

Then on the switched side, (1) a cable back to the starter and (2) power to the Ron Francis harness.

[stuchman1]

Thank you! As always, so helpful. Two follow-up questions:

- So we're really only using one side of the two-pole cutoff, correct?

- Dumb question but when you say power to the RF harness, which wire is that?

Thank you for your wisdom!
Sascha

[edwardb]

Thank you! As always, so helpful. Two follow-up questions:

- So we're really only using one side of the two-pole cutoff, correct?

- Dumb question but when you say power to the RF harness, which wire is that?

Thank you for your wisdom!
Sascha

That's what I did. Only used one side of the switch. The other side is to switch the alternator which is useful in some applications and required by some sanctioning bodies for competition. But I determined for the Coyote it doesn't add anything and isn't necessary. Your choice.

Power for the RF panel is the two large red wires with ring terminals -- RED - BATTERY FEED and RED - IGN SW -> SOL. The RED - ALTERNATOR FD is in the same group and typically attached at the same place. This is where it maybe gets confusing. The RF wiring diagram indicates these are for the starter solenoid. With battery power at the starter solenoid, that's one place you could pick up the RF power. But with the previous discussion about wiring in a master disconnect, there's really no reason to route those wires down to the physical starter solenoid. You have all the power you need at the switch. My approach is to take the wire from the switch to a bus bar behind the dash and attach the RF wires there.

There's no one way to wire these things. I'm trying to help you understand but you're also getting a dose of how I've done it. Others have done it differently. The important thing is for you to understand what's going on and then decide what's best for you. Highly recommend studying the wiring diagram in the RF wiring manual. It maybe seems complicated but it's not that bad. Really. You may want to ask for help from other builders in your area. You're not alone. Many builders cite wiring as their most difficult aspect of the build. Good luck.

[stuchman1]

That is so helpful. I get it. Thank you again! Sascha