2021 Bronco AUX Switches Wiring Diagram, Video, Discussions

[Efthreeoh]

Anyone know the actual load rating/fusing of each switch?

It's been posted in the thread:

AUX 1 = 25A @ 12VDC
AUX 2 = 15A @ 12VDC
AUX 3 = 10A @ 12VDC
AUX 4 to 6 are each 5A @12VDC

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[Efthreeoh]

The diagram prepared by @swooshdave is brilliant!

Now we can see more clearly how Ford has given us three circuits that are prewired back to the power box. They are B1, B2, and C. You can always use circuits D and/or E, but in doing so you use up B1 and/or B2.

I like how this design is way more than most buyers will ever use. Big thank you to Ford!

I also like how this requires careful thought as to how circuits will be used. You would be wise to separate in your mind the “need to have” versus “nice to have” gear and the preferred placement of each. Finally, will be the amps needed for each device, so you know where to connect in the power box.

With this new vision in mind, my tentative plan is outlined below.
Circuit B1 = GMRS Radio
Circuit B2 = TBD, either passenger compartment air compressor or link into Circuit E for rear chase light.
Circuit C = Fog lights.
Circuit D = No plans to use currently.
New Circuit F = Pod lights.
New Circuit G = Winch
New Circuit H = TBD, air compressor in the engine compartment.

This plan requires that I hold off using Circuit B2 and Circuit E until the air compressor location is determined.

Also in this plan, I may not have a rear chase light via Circuit E since the air compressor would need circuit B2 and perhaps Circuit E. In that case, I will explore using the new circuit H for a low-mounted light bar on the front bumper.

For me, lots of options and no limitations. Nice, real nice!

The three (3) pre-run circuits are all 16AWG wire which can be loaded to 25 amps, yet only two (2) of the switches are 16 gage wire, with one switch fused at 25A and the other at 15A. The other four switches are 18AWG, fused at (1) 10A and (3) at 5A.

Seems mismatched to me unless relays are used.

 

[ZackDanger]

Lastly the pictograph says the switches are labeled AUX 1 to 6 but refer to them as "Relays", so does that mean there are relays in the under-hood junction box (Fuse Box A)?

The 6 circuits under the dash are tied to the switches but through relays and fuses. You flip the switch but the power to your device isn’t going through it. The power is being fed through a relay for you

The three (3) pre-run circuits are all 16AWG wire which can be loaded to 25 amps, yet only two (2) of the switches are 16 gage wire, with one switch fused at 25A and the other at 15A. The other four switches are 18AWG, fused at (1) 10A and (3) at 5A.

Seems mismatched to me unless relays are used.

See above. Since the power circuits are being supplied through the relay/fuse, they have different ratings.

All the runs from the power distribution point to the rest of the vehicle are 16ga to accommodate the biggest draw you have, and you don’t have to worry where you place your devices (as long as the original switch circuit is rated for it).

 

[JaxGtc]

Since all of the switches are hot with ignition, what would it take to make one of them always hot for a dash cam?

 

[ZackDanger]

Since all of the switches are hot with ignition, what would it take to make one of them always hot for a dash cam?

Too much work. Better to just tap into an always hot circuit under the dash. Dashcams use so little power you don’t need to run a relayed Source from the engine compartment.

There’s even a few Ford dash cams available that come with a hardwire kit that plugs in under the dash. (I believe they take power from the OBDII port)

 

[Markubis]

Well done Ford!
I initially thought the switches were just wired to a distribution box. Adding the extra wired circuits to different sections gets a kudos.
Also, I love how easily the glove box can be dropped down. Another kudos to you Ford.
Well thought out.

And now I have to add the aux switches.....just because.

 

[Efthreeoh]

They only need to be connected if you intend to use them. Since there are 4 different amp ratings for the switches, how does Ford decide which one to connect to?

They should have sized all the switches the same at 16AWG. If the owner wants load protection at less amperages, he just swaps in lower rated fuses.

 

[Efthreeoh]

The 6 circuits under the dash are tied to the switches but through relays and fuses. You flip the switch but the power to your device isn’t going through it. The power is being fed through a relay for you



See above. Since the power circuits are being supplied through the relay/fuse, they have different ratings.

All the runs from the power distribution point to the rest of the vehicle are 16ga to accommodate the biggest draw you have, and you don’t have to worry where you place your devices (as long as the original switch circuit is rated for it).

That doesn't make sense. If all 6 switches fire relays to power the circuits then 18AWG is all that is needed. The trigger side of a relay doesn't need 25 amps.

25A and 15A tells me the device is powered from the switch directly.

 

[ZackDanger]

That doesn't make sense. If all 6 switches fire relays to power the circuits then 18AWG is all that is needed. The trigger side of a relay doesn't need 25 amps.

The 6 leads in the power distribution area that you tap into are already coming out of the relays. Some are rated up to 25amps.

We don’t actually ever see the trigger side of the relay as the consumer.

Ford is just saying “Switch 1 is rated for 25amps” and under the hood there is a wire labeled “switch 1” that is rated for 25 amps.

Am I confused?

::EDIT::

Wait, I think your point is that if the power distribution is relayed already why aren’t they all rated for 25amps?

Yes. I agree.

My only guess is that it’s a cost savings somewhere... I’m also upset that only two leads were passed through the firewall, and then only a single wire was run from the glove box to the rear and one up to the roof.

IMHO, they should have continued 6 leads to the glove box, then from there 2 to the top of the windshield and probably 3 to the rear.

Perhaps there is a power drop behind the glove box as well, with ACC, B+, and GND... which would calm me down a bit.

 

[Portapot]

Honestly, these wires look very small to be powering something such as an amplifier. Unless you are talking about a small amplifier 100w or less.

I don't see how a thin wire like that can pull 25 amp... (aux 1)

Peter

edit: here's some reference charts. 25A requires 12 AWG. and 12 AWG has wire thickness of 0.08 inch (just over 5/64), or 2.05mm in metric. I may be way off eyeballing the wires in the video, but it doesn't look anywhere near thick enough.

Assuming a 12V system, I would need 41 amps to drive a 500 watt amplifier, so I assume an independent line would need to be setup...i should have done a little research before posting ;o)

 

[Beachin 74]

Good info on this thread!
Nice view of the cabin air filter at 3:38.

 

[Efthreeoh]

The 6 leads in the power distribution area that you tap into are already coming out of the relays. Some are rated up to 25amps.

We don’t actually ever see the trigger side of the relay as the consumer.

Ford is just saying “Switch 1 is rated for 25amps” and under the hood there is a wire labeled “switch 1” that is rated for 25 amps.

Am I confused?

::EDIT::

Wait, I think your point is that if the power distribution is relayed already why aren’t they all rated for 25amps?

Yes. I agree.

My only guess is that it’s a cost savings somewhere... I’m also upset that only two leads were passed through the firewall, and then only a single wire was run from the glove box to the rear and one up to the roof.

IMHO, they should have continued 6 leads to the glove box, then from there 2 to the top of the windshield and probably 3 to the rear.

Perhaps there is a power drop behind the glove box as well, with ACC, B+, and GND... which would calm me down a bit.

Just to be clear I'm not arguing with you about it because you may be correct and I am wrong . I'd be in agreement with you if all the wires from the firewall (assuming they come directly from the switches) were all 18AWG leads, but they are 2 ea. at 16AWG and 4 each at 18AWG, which indicates the switches themselves are rated by load capacity. Again, the data we have so far is obviously not all the information we need to figure out the circuitry. One has to assume the switches are fused out of whatever distribution box they are powered from. It would be nice to see the entire circuit from BATT+ to terminated lead at the engine bay.

What I don't get is if most of the Ford accessories are pre-engineered and one is a light bar on the roof, then why not just route the wire in the windshield header directly from the switch? Why route it out of the firewall, into the junction box, back over to the glove compartment and back up to the header via the right A-pillar back to just inches away from the switch?

 

[mrjerry469]

Great news I didn't know that wiring was run through out the vehicle easier for me bc I have a bad hand.

 

[Trooper]

Any thoughts on how this set up might lend itself to aftermarket heated seats? (for those of us who don't have access to the mid package?). Would it be possible to wire them to the aux system?

 

[1979]

Leave it this group of people to complain about Ford giving extra, unexpected features.

Pre-run circuits are a good thing!

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