Can Trailer Wiring Harness be Connected to 12 Volt Power Outlet Instead of Battery on Toyota Sienna

Question

Question:

Can the 12-volt power on a 4-blade vehicle to 7-blade trailer adapter be connected to a 12-volt auxiliary socket. My brother’s Toyota Highlander 4-way flat plug could not power the lights on my 2005 Aliner with a 7-way. I assume it was missing power. Can I provide power to the connection via an interior auxiliary plug rather than wire to the car battery. He only wants to borrow the trailer for a weekend. Part no.: 37185 Adapter 4-Pole to 7-Pole and 4-Pole

asked by: Jack D

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Expert Reply:

The 4- to 7-Way adapter # 37185 will need to have the 4-Way plugged into it and the white wire grounded to the frame of the vehicle. The other wires (black for 12 volt power, blue for electric trailer brakes, and purple for reverse lights) don't have to be connected if all you want are the trailer lights to function. If you did want all of those functions to work I recommend # ETBC7 because it comes with the wiring and accessories needed to wire it all up so it is fully functional and so you can add a brake controller such as # 90885.

Four-way powered trailer wiring harnesses that require a direct connection to the battery are not tested or rated for any alternate installation method. Installing it by attaching the power wire to a power outlet 12 volt wire will void the warranty. Also many times those outlets are not the only component on the fuse and/or there could be a relay that has other functions. So if the wiring harness is drawing power and whatever else is fused with it or that uses the same relay is drawing power then it can cause more costly electrical problems.

You probably know already that routing the power wire to the vehicle battery isn't difficult; it just takes time. I have included a link to a help article I wrote that offers some tips for routing the power wire for you.

On powered harnesses, because they attach directly to the vehicle battery they have power all the time but unless something is plugged into the connector and drawing power it doesn't run down the battery.

If I was choosing a wiring harness for a 2011 to 2016 Toyota Sienna I would go with # 118498 because we hear about less problems with the Tow Ready brand. I have included a link to a video showing an example installation for you.

expert reply by: Michael H

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Answer 1

I strongly recommend running the 12 volt power wire from the Curt Wiring Harness, #C59496, directly to the vehicle battery. The 12 volt accessory circuit was not designed to support the additional load of a trailer wiring harness. A wiring harness…

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Answer 2

You picked a good vehicle. The Grand Caravan is one of the best available minivans out there from a towing standpoint. The amount you can tow with the vehicle will decrease as you add passengers. With a driver and one passenger plus their luggage,…

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Answer 3

All of the available trailer wiring harness available for a 2011 Toyota Sienna, including the CURT wiring, #C56106, install by connecting in line with the tail light wiring connectors located behind each of the vehicle tail lights. A power wire will…

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Answer 4

The difference between the Class II and Class III hitches has to do with their Gross Trailer Weight (GTW), their Tongue Weight (TW), and their Hitch Receiver Size. Class II trailer hitch receivers have a 1-1/4 inch receiver and can be rated up to…

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Answer 5

When we test fit hitches, we take note of above ground height of the inside top of the receiver tube. When the size of the receiver (2 inch or 1-1/4 inch) and the thickness of the lip around the receiver (1/4 inch) is deducted, you get a good…

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Answer 6

Powered trailer wiring harnesses are not tested or rated for any alternate installation method. Installing it by attaching the power wire to a power outlet 12 volt wire will void the warranty. Also many times those outlets are not the only component…

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Answer 7

Rather than change the coupler, the easiest option is to change the size of the ball ON YOUR BALL mount. If your coupler currently uses a 1-7/8 inch ball and your towing vehicle has a hitch and ball mount with a 2 inch ball, you can use an…

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Answer 8

As long as you have the needed wheel well and trailer frame clearance, there is no reason that you couldn't go to a larger tire size from your existing 5.30-12 tires. The next size up from what you have is going to be with an ST175/80-13 size…

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Answer 9

The 5.30-12 tires, being wider, are going to make more contact with the road. This means that the noise, and heat build up will be higher than a 4.80-12 tire but the rolling resistance will actually be less because the tire is larger diameter. The…

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Answer 10

Bearing Buddy pumps grease into the center of the hub all the way back to the grease seal. A double lip seal should be used to prevent grease from blowing out the seal when added. When the hub and seals and bearings are first assembled, they should…

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Answer 11

The Taskmaster Provider ST175/80R13 Radial Trailer Tire w/ 13 Inch White Wheel #TA43RR should work well for replacing the smaller 4.80X12, 5 on 4-1/2 inch tire and wheel currently on your trailer. This tire has a ply rating of 16 and a 1,360 pound…

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Answer 12

I did a bit of research and the information that I found shows the 1997 Shoreland'r OMC-V1928A / OMC-GV1928A having a 10" black poly fender. When it comes to a replacement fender of this size, I recommend either the Style B Single Axle…

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Can Trailer Wiring Harness be Connected to 12 Volt Power Outlet Instead of Battery on Toyota Sienna

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