Running a circuit through the fuse box: Is it possible?

[Oingoboingoagogo]

Good morning everyone,

This is my first post. Happy to be here. I have spent a ton of time on this and other forums for my 2020 Ranger, and my previous 2000 Ranger. But today I have been forced to make an account, because it seems no one has asked the following question:

Does anyone know of an unpowered connection between the engine bay and cabin fuse boxes? If you'd like to know why I'm looking, read on.

I am installing an ooga horn in my new Ranger. It is a very silly horn—like the really old Fords have. It's a crazy sound, so I'm not going to replace my main horn. Instead, I am installing the horn under the hood, with a relay, and putting a small illuminated button inside the cab near the center cupholders.

My instinct, like most, is to run a wire from button to relay via the firewall. But I've been thinking... there is already a mess of wires running through the firewall via the fuse boxes. Isn't it possible that there is an unpowered connection between a fuse port in the cab, and another fuse port under the hood? If so, it would be possible to run the circuit without much fuss.

I have scoured this and other forums looking for tips, and it looks like no one has asked before. Am I crazy? It seems strange to me that with all of the unused fuses/terminals in the boxes, that there wouldn't be at least a couple of continuous connections that don't receive 12V power.

P.S. I am still designing the mount to keep the horn secure. Here's an image of the horn sitting in my 3D printed prototype (orange)!

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[ControlNode]

It is possible, but you'll really best served by getting the wiring diagram for your truck and looking for circuits that support options your truck may be lacking. With as many modules now use CAN to communicate there are less unused wires between major areas though. But it is possible still. But, is really an area most don't bother because for less than half the time researching all of that we can run a new wire and be 100% sure it will work.

 

[Oingoboingoagogo]

Thanks for you insight, ControlNode. Considering how popular these trucks are, I am surprised no one else has asked, let alone attempted the job! All it takes is one person figuring it out and posting the results, then the research time is zilch.

But I see your point. I will run the wire if I have to; it seems more challenging in this 2020 Ranger than it was in my old 2000. I disagree, however, with the idea that I can "be 100% sure it will work." It's only when I'm 100% sure something will work... that it doesn't!?

 

[Oingoboingoagogo]

Anyone else? I'm curious if anyone here has heard of someone doing this... in any vehicle... ever.

 

[got3fords]

If you are never going to blow both horns at the same time, can you just tap into the stock horn wiring?

 

[airline tech]

The answer to your question - No there are no circuits (unused) with wiring already ran on the Lariat.

However, there are a number of (unused) spots to tap for power on the BCM & BJB Fuse Boxes.
Note: You will have to check your owner's manual for a list of fuses as a possible tapped source.
As there are a mixture (I think) of

1. Fuse installed - and Not Used
2. Fuse Not Installed -(Contact Pins) installed - (Not Used)
3. Blank Spot (No Terminals) for Power in the Fuse Location

You also have the option at least for the switch & relay coil power to just tap any switched fuse power source, the Horn itself will need a (Unused 20 Amp +) source or direct to the battery with an inline fuse, because tapping into an existing source for that high of amp draw will overload the circuit and blow the fuse.

Note: I have been working on a list for these (Not Used) Locations, but the biggest question is and uncertainty, is the spot blank or is it wired internally. (Fuse Feeding the Connector Pin) at the Fuse Box.
Note here you have an option (if wired) easy and just add a tap - to tap off the power or locate the connector & pin that the fused side is feeding and then ADD a terminal pin to that connector

To help understand how the BCM fuse box is wired, there are very few (Power Inputs) as the BCM Mega Fuse feeds the majority of the power input with the exception of the High Amperage power sources which are ran separately into it.
The lower amperage fuses off of the BCM (Fuse Box) are secondary to the Mega Fuse

I suggest instead of focusing on (Horn) Install, search through the lighting threads and see where others have tapped for power sauces and supplement those sources with your horn.
I suspect you are needing a 20-30 Amp source for the horn, and you could tap a lower power source for the switch (lighted) & relay coil.

Sorry, I have not tapped into power for anything, I would have to physically check what's available vs what the wiring diagrams show.
@OFC Ranger comes to mind with using lots of Power Tapping & Relays, reading his extensive lighting mods or I believe @Msfitoy is another member, who has added extensive lighting mods.
I am sure I can help, but some direction from others who have already been down the road for what works and what doesn't may make this easier. (Tapped Sources & The Sensitive BCM) power outputs.

I hope this at least helps some, this is a doable mod, I just do not see anybody who has done an electric horn (addition) I have seen some with adding an Air Horn though.

 

[OFC Ranger]

Outside of a Tremor model with the factory aux panel the answer is no.

 

[Msfitoy]

I use Trigger 6 which is kind of like installing a separate circuit box with it's own set of fuses...it taps directly to the battery terminals and seems to be working flawlessly for the past 130K miles...

 

[Oingoboingoagogo]

Hi all,

Thank you for your responses.

@got3fords I don't think that would solve my problem in this case. Clever idea though.

@airline tech Okay, I'm hearing from you that there are no unpowered circuits that I can take advantage of between the fuse boxes. Thank you for the suggestions re: tapping a fuse for the horn switch, and the note about high amperage for the horn itself. I have made these considerations as well.

For the record, I understand the electronics work involved here, and I have no problem tapping low amp power for the switch in the cab, and running a wire from the cab to a relay under the hood, and triggering high current right off the battery for the horn to sound. I just wanted to see if anyone was aware of some unused unpowered circuits between the fuse boxes, which would save me the trouble of running a new wire through the firewall.

@OFC Ranger Your note about the Tremor Aux board is interesting. There must be extra wires bundled in the main harness that runs through the firewall in the Tremor. Otherwise... that would indicate that there is in fact an unused, unpowered circuit in my truck, since I believe all of the models use the same base electrical systems and boxes.

@Msfitoy Cool accessory. I'm guessing that requires wiring through the firewall though!

 

[LawnMM]

@Msfitoy Cool accessory. I'm guessing that requires wiring through the firewall though!

It's wireless. Wired in the engine compartment obviously, wirelessly controlled.

 

[treeranger]

Sounds like a fun project! Good luck with the install.

 

[OFC Ranger]

@OFC Ranger Your note about the Tremor Aux board is interesting. There must be extra wires bundled in the main harness that runs through the firewall in the Tremor. Otherwise... that would indicate that there is in fact an unused, unpowered circuit in my truck, since I believe all of the models use the same base electrical systems and boxes.

No, the additional wiring for the Tremor aux panel is in fact specific to the Tremor's equipped with it. That includes the the addition relay box and associated wiring harness to bridge the panel to the battery in the engine bay, which again, is not present on any other model from the factory.

That tremor only upfitter box contains not only the relays, but its fuses as well.

To my knowledge the only present power source that is "unused" on the entire truck is in the rear fender well of the bed is a line connector for creating a bed accessible 12v source, but even that has no tie in to a control in the cabin at all. It is an always on channel when the truck is powered on.

Trust me, when I had my Ranger I was very intimately detailed with the 12v system - what you are looking for does not exist.

 

[Msfitoy]

Hi all,

Thank you for your responses.

@got3fords I don't think that would solve my problem in this case. Clever idea though.

@airline tech Okay, I'm hearing from you that there are no unpowered circuits that I can take advantage of between the fuse boxes. Thank you for the suggestions re: tapping a fuse for the horn switch, and the note about high amperage for the horn itself. I have made these considerations as well.

For the record, I understand the electronics work involved here, and I have no problem tapping low amp power for the switch in the cab, and running a wire from the cab to a relay under the hood, and triggering high current right off the battery for the horn to sound. I just wanted to see if anyone was aware of some unused unpowered circuits between the fuse boxes, which would save me the trouble of running a new wire through the firewall.

@OFC Ranger Your note about the Tremor Aux board is interesting. There must be extra wires bundled in the main harness that runs through the firewall in the Tremor. Otherwise... that would indicate that there is in fact an unused, unpowered circuit in my truck, since I believe all of the models use the same base electrical systems and boxes.

@Msfitoy Cool accessory. I'm guessing that requires wiring through the firewall though!

Actually no...the power switch for the Trigger 6 is either by their wireless switch box and/or Bluetooth app on phone...

 

[Motorpsychology]

Anyone else? I'm curious if anyone here has heard of someone doing this... in any vehicle... ever.

You can buy a fuse tap to install into an existing fuse location. One was used one when the dealer installed seat heater pads on my STX. Be sure that the fuse tap is for the same type of fuse that was originally in that location. A fuse tap allows two devices to run independently on the same circuit. do not power the horn from a circuit that has a lower rating than the horn calls for. find the fuse location and type in your Owners Manual. Your ooga horn probably has a relatively high current draw that is relay controlled.

 

[ControlNode]

You can buy a fuse tap to install into an existing fuse location. One was used one when the dealer installed seat heater pads on my STX. Be sure that the fuse tap is for the same type of fuse that was originally in that location. A fuse tap allows two devices to run independently on the same circuit. do not power the horn from a circuit that has a lower rating than the horn calls for. find the fuse location and type in your Owners Manual. Your ooga horn probably has a relatively high current draw that is relay controlled.

I think you missed at least 90% of what the OP was asking about doing.

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