- First Name
- Michael
- Joined
- Dec 31, 2020
- Threads
- 6
- Messages
- 111
- Reaction score
- 371
- Location
- Monterey, CA
- Vehicle(s)
- Bronco Sport Badlands, Fiesta ST
- Thread starter
- #1
Trailer Wiring Install for Bronco Sport Using Factory Power Circuit (Part One – Research)
*****
NOTE: The “Part One” post is a bit of back-story on the research I did on installing an aftermarket 4-way trailer lighting system on my Bronco Sport Badlands using Ford’s factory trailer power supply circuit. The actual installation begins with Part Two. If you have no interest in the “why” and want to just see the “how”, feel free to skip this section.
NOTE 2: I have a tendency to be somewhat “thorough” when making modifications to my rides (my wife occasionally has used other terms, which I won’t deny), usually with the goal of making the install as clean, professional, and post-install serviceable as possible. As such this is being provided as a guide in the hopes that others don’t have to repeat the time, research, and pain to do something similar. It isn’t intended to be the be-all-end-all guide and no warranty on accuracy, repeatability, or your skills in performing a similar install is expressed or implied. In other words, Caveat Emptor ?
NOTE 3: For reasons that aren’t really relevant to this post, I did not get the factory trailer package. While I think my installation here is of great quality and potentially offers some upgrade capability that Ford doesn’t, in nearly all cases you are better off ordering/buying the factory tow package for your BS. It will come with full warranty support and won’t come with the time, effort, skinned knuckles, and the foul language that a DIY solution does.
*****
When I received my Badlands in December of 2020, it didn’t come with the factory trailer package, which was something that was high on my desire list (and was in the original order, but…). As such, I did want to get an as-good-as-factory setup as possible and began doing the research on what might be the best way to go about that.
Originally at the encouragement of my Dealer (as I did gripe about my missing factory tow package) I ordered the Dealer Tow Package, only to see it backordered, replaced with a new package P/N, and, near as I can tell never actually becoming available in any notable quantities. So once a Curt hitch became available, I ordered and installed that instead. I won’t document the Curt hitch installation as there are plenty of posts here as well as online instructions with cover that well. Suffice to say it was an easy install and the quality is what one would normally expect from Curt (Very Good).
At the time though I held off on installing the wiring as most kits I had seen at the beginning of this year were generic in nature and, in the past on Ford vehicles, I had found that there was at least a partial installation of the wiring for a 4-way connector (in some cases such as the early Ford Escape, it was just a matter of adding a relay and a wiring pigtail as the wiring harness was otherwise complete).
To get the answer to that I needed to do some research over the summer…
The first clue that Ford may have left at least something that could be connected to is in the Owner’s Manual. In the Fuses section of the manual, there is a Fuse listed as being located in the Battery Junction Box with a 40 amp service for the “Trailer Tow Module”:
And, lo-and-behold, upon opening the Box, I found that the location and the fuse were both present/installed on my non-factory-equipped Badlands:
So, this gets interesting… The question now is how far does the wiring for that circuit go and would it even be possible to add the missing modules and connectors?
Next step was to find a way to get a shop manual and wiring diagram. Those started popping up on eBay in the spring and I added a DVD to my library. In the manual there is a section covering the wiring for the Trailer Tow Module, with 3 sections of wiring harness related to it. Section one runs from the Battery Junction Box to a connector located just behind the glove box on the passenger side. Section two runs from the glove box location to just above the right rear wheel-well (internally, behind the interior cargo panel). Section three runs from that location to a junction point under the car that would have provided the 4-way plug. Also, in the wiring diagram it was noted that the power wire for the Trailer Tow Module was a pretty hefty 10 gauge Blue/Red Stripe wire.
A cursory examination made it clear that section three of the wiring harness wasn’t installed on my Badlands. More disappointing was that, when examining section two of the wiring harness, it was clear that the heavy gauge wire was missing, meaning that Ford does use a different center section (section two) wiring harness for Bronco Sports without the factory tow package.
But since the Fuse is present, perhaps at least the wiring coming out of the Battery Junction Box is present as well?
The good news is that the elusive Blue/Red Stripe wire does indeed come out of the Battery Junction Box, runs through the firewall, and terminates into the harness connector behind the glove box. It simply ends there when connected to the next section of harness and therefore is unused. This meant that it should be possible to tap that line without having to penetrate the firewall or running a direct-to-battery connection.
The last item of good news was, once Bronco Sport support was added to FORScan, a readout of the program settings revealed that the Trailer Sway Control was present and enabled on my Badlands (something that appears to be true for most/all 2021 Bronco Sports, regardless of trailer package status).
This would seem to indicate that it should be possible to do a pretty clean install that would be a close match to what Ford offered, using the actual fuse/circuit that Ford designed for the trailer wiring.
Now, on to the actual installation (Part Two)
*****
NOTE: The “Part One” post is a bit of back-story on the research I did on installing an aftermarket 4-way trailer lighting system on my Bronco Sport Badlands using Ford’s factory trailer power supply circuit. The actual installation begins with Part Two. If you have no interest in the “why” and want to just see the “how”, feel free to skip this section.
NOTE 2: I have a tendency to be somewhat “thorough” when making modifications to my rides (my wife occasionally has used other terms, which I won’t deny), usually with the goal of making the install as clean, professional, and post-install serviceable as possible. As such this is being provided as a guide in the hopes that others don’t have to repeat the time, research, and pain to do something similar. It isn’t intended to be the be-all-end-all guide and no warranty on accuracy, repeatability, or your skills in performing a similar install is expressed or implied. In other words, Caveat Emptor ?
NOTE 3: For reasons that aren’t really relevant to this post, I did not get the factory trailer package. While I think my installation here is of great quality and potentially offers some upgrade capability that Ford doesn’t, in nearly all cases you are better off ordering/buying the factory tow package for your BS. It will come with full warranty support and won’t come with the time, effort, skinned knuckles, and the foul language that a DIY solution does.
*****
When I received my Badlands in December of 2020, it didn’t come with the factory trailer package, which was something that was high on my desire list (and was in the original order, but…). As such, I did want to get an as-good-as-factory setup as possible and began doing the research on what might be the best way to go about that.
Originally at the encouragement of my Dealer (as I did gripe about my missing factory tow package) I ordered the Dealer Tow Package, only to see it backordered, replaced with a new package P/N, and, near as I can tell never actually becoming available in any notable quantities. So once a Curt hitch became available, I ordered and installed that instead. I won’t document the Curt hitch installation as there are plenty of posts here as well as online instructions with cover that well. Suffice to say it was an easy install and the quality is what one would normally expect from Curt (Very Good).
At the time though I held off on installing the wiring as most kits I had seen at the beginning of this year were generic in nature and, in the past on Ford vehicles, I had found that there was at least a partial installation of the wiring for a 4-way connector (in some cases such as the early Ford Escape, it was just a matter of adding a relay and a wiring pigtail as the wiring harness was otherwise complete).
To get the answer to that I needed to do some research over the summer…
The first clue that Ford may have left at least something that could be connected to is in the Owner’s Manual. In the Fuses section of the manual, there is a Fuse listed as being located in the Battery Junction Box with a 40 amp service for the “Trailer Tow Module”:
And, lo-and-behold, upon opening the Box, I found that the location and the fuse were both present/installed on my non-factory-equipped Badlands:
So, this gets interesting… The question now is how far does the wiring for that circuit go and would it even be possible to add the missing modules and connectors?
Next step was to find a way to get a shop manual and wiring diagram. Those started popping up on eBay in the spring and I added a DVD to my library. In the manual there is a section covering the wiring for the Trailer Tow Module, with 3 sections of wiring harness related to it. Section one runs from the Battery Junction Box to a connector located just behind the glove box on the passenger side. Section two runs from the glove box location to just above the right rear wheel-well (internally, behind the interior cargo panel). Section three runs from that location to a junction point under the car that would have provided the 4-way plug. Also, in the wiring diagram it was noted that the power wire for the Trailer Tow Module was a pretty hefty 10 gauge Blue/Red Stripe wire.
A cursory examination made it clear that section three of the wiring harness wasn’t installed on my Badlands. More disappointing was that, when examining section two of the wiring harness, it was clear that the heavy gauge wire was missing, meaning that Ford does use a different center section (section two) wiring harness for Bronco Sports without the factory tow package.
But since the Fuse is present, perhaps at least the wiring coming out of the Battery Junction Box is present as well?
The good news is that the elusive Blue/Red Stripe wire does indeed come out of the Battery Junction Box, runs through the firewall, and terminates into the harness connector behind the glove box. It simply ends there when connected to the next section of harness and therefore is unused. This meant that it should be possible to tap that line without having to penetrate the firewall or running a direct-to-battery connection.
The last item of good news was, once Bronco Sport support was added to FORScan, a readout of the program settings revealed that the Trailer Sway Control was present and enabled on my Badlands (something that appears to be true for most/all 2021 Bronco Sports, regardless of trailer package status).
This would seem to indicate that it should be possible to do a pretty clean install that would be a close match to what Ford offered, using the actual fuse/circuit that Ford designed for the trailer wiring.
Now, on to the actual installation (Part Two)
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