Converting 4-wire trailer plug to 7-pole on Outback - Fiberglass RV



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Old 02-10-2019, 05:35 PM   #1
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Name: Ruth
Trailer: 2014 Scamp 13'
Wisconsin
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Converting 4-wire trailer plug to 7-pole on Outback

My new-to-me 2014 13' Scamp has electric brakes.

The tow vehicle, a 2012 Subaru Outback 2.5i has 4-wire flat plug. Where do I go to have the wiring converted to a 7-pole so I can use the trailer brakes?

U-Haul, RV World, Custom RV Services, Scamp at Backus, other?

Thanks in advance for directing me on the next step!
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Old 02-10-2019, 06:12 PM   #2
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The 4-Pin flat connector does not have the wiring necessary for hooking up to electric brakes. Most tow vehicles are equipped with either a factory installed or an aftermarket electric brake controller and a 7-pin plug-in connector. You can have a controller installed in your tow vehicle, along with the 7-Pin connector you'll also need, and most any place that sells and services trailers should be able to get you set up.

And as an aside, I don't know if Scamp pre-wires their trailers for reverse lights, (I know Casita does,) but if they do have reverse lights on the Scamps, then it is most probably hooked to the center, (#7 Extra Aux. Terminal,) Pin in the connector. If you have to back up at night, it's nice to be able to see while backing. I just thought I'd mention it, because a lot of aftermarket controller/connector installers don't usually hook that one up in your tow vehicle unless you ask for it to be done. The logic is that many small utility trailers may have electric brakes, but don't have reverse lights. Most travel trailers do.
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Old 02-10-2019, 06:41 PM   #3
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Get this kit, it includes everything you need to convert 4pin connector to RV 7 pin. https://www.etrailer.com/Accessories...ler/ETBC7.html
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Old 02-10-2019, 09:39 PM   #4
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California
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I wound up getting a Tekonsha Prodigy RF Wireless brake controller for use with my 2010 Subaru Forester. The wireless controller mounts on the trailer tongue and eliminates the need to hard wire a dash mounted brake controller into your Subaru's brake light circuit for a brake signal. That makes the job MUCH simpler. You will still have to add one heavy 10 ga. charge wire (with appropriate circuit protection) to a 9 pin plug mounted at the bumper / hitch. I ran my 10 ga. wire to the hot post on the car battery. You can get 9 pin plug receivers that will accept your four pin flat connector on its back side to power up your tail and turn signal lights through the 9 pin connector. Any decent trailer or RV dealer should have a tech to install it for you.

Don't be turned off by the higher price of the wireless brake controller. It will save it's additional cost through decreased labor. I also love the fact that I didn't have to touch my Forester's electrical wiring with this controller.
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Old 02-11-2019, 08:34 AM   #5
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Name: Justus
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Quote:
Originally Posted by Casita Greg View Post
The 4-Pin flat connector does not have the wiring necessary for hooking up to electric brakes. Most tow vehicles are equipped with either a factory installed or an aftermarket electric brake controller and a 7-pin plug-in connector. You can have a controller installed in your tow vehicle, along with the 7-Pin connector you'll also need, and most any place that sells and services trailers should be able to get you set up.

And as an aside, I don't know if Scamp pre-wires their trailers for reverse lights, (I know Casita does,) but if they do have reverse lights on the Scamps, then it is most probably hooked to the center, (#7 Extra Aux. Terminal,) Pin in the connector. If you have to back up at night, it's nice to be able to see while backing. I just thought I'd mention it, because a lot of aftermarket controller/connector installers don't usually hook that one up in your tow vehicle unless you ask for it to be done. The logic is that many small utility trailers may have electric brakes, but don't have reverse lights. Most travel trailers do.
That's some good info. On the eTrailer installation walkthrough for my vehicle, the guy doing the installation says this:

Quote:
Now the purple wire that's coming out of the back of the plug, this is going to be for a reverse light signal coming to our plug. Typically, you'll use this for a marine style application if you have surge brakes. We are not going to be using it, so we're just going to snip that off. We'll leave a little bit there in case the customer ever decides they want to add it, but for right now just kind of tuck this away."
So that's interesting to me that you wouldn't just go ahead and hook up that wire while you've got the vehicle up on a lift. It looks like the best place to tap into the reverse line is in the back behind an access panel; maybe the guy doing the video just didn't want to deal with another penetration and fishing the wire up into the trunk space.

Your diagram showed a yellow wire as #7 (aux), but it appears there is not a standard color for this. The blade arrangement is standard, so you can use a multimeter or circuit tester to test continuity and determine which wire connects which blade for your particular plug.

To Ruth, you should call around to see who will do the wiring for you and if they will use parts that you provide before you buy parts. I recall seeing mixed reviews for U-Haul, and that some locations won't do it or will only do it for certain vehicles. My dealership won't do it because Toyota doesn't make an OEM 7-way harness for my vehicle and they won't install aftermarket parts; I think Subaru would be much the same, as few Outback owners would need a 7-way connection. So give those places you mentioned a call; you can also try independent auto shops.
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Old 02-11-2019, 04:17 PM   #6
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Quote:
Originally Posted by Justus C View Post
That's some good info. On the eTrailer installation walkthrough for my vehicle, the guy doing the installation says this:
So that's interesting to me that you wouldn't just go ahead and hook up that wire while you've got the vehicle up on a lift. It looks like the best place to tap into the reverse line is in the back behind an access panel; maybe the guy doing the video just didn't want to deal with another penetration and fishing the wire up into the trunk space.

Your diagram showed a yellow wire as #7 (aux), but it appears there is not a standard color for this. The blade arrangement is standard, so you can use a multimeter or circuit tester to test continuity and determine which wire connects which blade for your particular plug.
What I did to hook up my reverse lights was to keep it simple. I just tapped into one of the existing reverse light wires going to one of my truck's reverse lights under the rear of the truck, and hooked it to the center pin of the 7-Pin Bargman plug-in connector on the rear bumper where it's mounted.
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Old 02-11-2019, 05:47 PM   #7
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Name: Jann
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Originally Posted by Casita Greg View Post
The 4-Pin flat connector does not have the wiring necessary for hooking up to electric brakes. Most tow vehicles are equipped with either a factory installed or an aftermarket electric brake controller and a 7-pin plug-in connector. You can have a controller installed in your tow vehicle, along with the 7-Pin connector you'll also need, and most any place that sells and services trailers should be able to get you set up.

And as an aside, I don't know if Scamp pre-wires their trailers for reverse lights, (I know Casita does,) but if they do have reverse lights on the Scamps, then it is most probably hooked to the center, (#7 Extra Aux. Terminal,) Pin in the connector. If you have to back up at night, it's nice to be able to see while backing. I just thought I'd mention it, because a lot of aftermarket controller/connector installers don't usually hook that one up in your tow vehicle unless you ask for it to be done. The logic is that many small utility trailers may have electric brakes, but don't have reverse lights. Most travel trailers do.
Recently I was discussing the standard 7 pin plug with our mechanic because of an electrical problem we think we have. He showed me 4 different 7 pin plugs that all have lights, brakes, etc in different locations on the plug. So they are not standard like we think. It is possible the tow vehicle doesn't match the trailer plug even on a 7 pin. Even the hot wire and the ground were in different places. When we bought our Casita and for a long time afterwards they were all standard. Guess something has changed. We had our brake controller done by an RV dealer. Fortunately our vehicle was prewired for the controller and a standard 7 pin connection on the back of vehicle.
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Old 02-11-2019, 06:50 PM   #8
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Name: Ruth
Trailer: 2014 Scamp 13'
Wisconsin
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Thank you everyone for your advice. I like the idea of having the reverse lights wired to function. I also like the idea of a wireless controller for simplicity. But it seems like I can't have both, right?

I will call around and see what U-Haul, RV World, and the specialty trailer place have to say about the project.

Ruth
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Old 02-12-2019, 08:49 AM   #9
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Name: Michael
Trailer: Casita 16ft.
California
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Originally Posted by RuthWI View Post
Thank you everyone for your advice. I like the idea of having the reverse lights wired to function. I also like the idea of a wireless controller for simplicity. But it seems like I can't have both, right?

I will call around and see what U-Haul, RV World, and the specialty trailer place have to say about the project.

Ruth
The reverse light and the brake controller, have nothing in common beyond their respective places on the 7 pin plug. This applies whether you use a conventional hard wired brake controller mounted in the tow or a wireless RF brake controller mounted on the trailer tongue.

Making a reverse light work on a trailer requires finding a power source from your reverse light system in your tow vehicle and herding that power through the proper pole on the 7 pin plug and on back to a reverse light(s) affixed to your trailer. You would have to do that with either type of brake controller. If having a reverse light is important to you it probably can be done. For me, it wasn't high enough on my priority list to want to cut into my stock vehicle
wiring loom to make it happen. But I have the love of my life for the past 38 years to stand back of the trailer with a flash light to guide me in.
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Old 02-12-2019, 12:38 PM   #10
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Originally Posted by Nor Cal Mike View Post
The reverse light and the brake controller, have nothing in common beyond their respective places on the 7 pin plug. This applies whether you use a conventional hard wired brake controller mounted in the tow or a wireless RF brake controller mounted on the trailer tongue.

Making a reverse light work on a trailer requires finding a power source from your reverse light system in your tow vehicle and herding that power through the proper pole on the 7 pin plug and on back to a reverse light(s) affixed to your trailer. You would have to do that with either type of brake controller. If having a reverse light is important to you it probably can be done. For me, it wasn't high enough on my priority list to want to cut into my stock vehicle
wiring loom to make it happen. But I have the love of my life for the past 38 years to stand back of the trailer with a flash light to guide me in.
Same here. reverse lights not a priority and don't want to void warranty. I use two of those free work lights from Harbor Freight. They are magnetic so I turn them on and stick them to the rear bumper of my boler. Instant reverse lights.
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Old 02-12-2019, 01:53 PM   #11
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Originally Posted by Alex Adams View Post
Same here. reverse lights not a priority and don't want to void warranty. I use two of those free work lights from Harbor Freight. They are magnetic so I turn them on and stick them to the rear bumper of my boler. Instant reverse lights.
Now that's an idea! Thanks!!
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Old 02-12-2019, 02:00 PM   #12
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I wouldn't stick the lights on the bumper. I'd use them left and right of where I wanted to place the trailer.
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Old 02-12-2019, 02:51 PM   #13
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Originally Posted by Glenn Baglo View Post
I wouldn't stick the lights on the bumper. I'd use them left and right of where I wanted to place the trailer.
I should have been more specific, I put each one towards the ends of the bumper. That way they illuminate behind and to the right and left sides of the trailer.
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Old 02-16-2019, 02:12 PM   #14
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Name: Tony
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Thermal breakers

So I had the same thing done to my wife’s 2015 Outback. We went to a local RV maintenance shop. Had to wait a month for our appointment. Anyway, he picked up the brakes lights, turn signals and lights (running and rear) from the flat four pin. He also ran a power wire from the battery to the 7 pin and another power wire from the battery to the dash for a brake controller along with another wire from the dash to the 7 pin for the brake controller.

I do have a question on the fuses used. He used two 30 amp thermal fuses mounted on the side wall of the engine compartment. One for the power line and one for the brake controller. They disconnect with too much current (ie heat) but are usable after they open if the current draw is acceptable. I think power needs to be removed for them to reset. That seemed fine to me, but is that standard? Is it safe?
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