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Trailer Wiring Harness Adapter Installation - 2010 Toyota Tundra

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How to Install a Wiring Harness Adapter on a 2010 Toyota Tundra

Today on this 2010 Toyota Tundra pickup, we are going to install part number 37185. Also, we are going to use an install bracket, part number 118136 from Tow Ready. In this case what we are going to do is we have our factory 4-pole lose from the vehicle. Our 7 and 4-pole down to our 4-pole adapter is going to go on the end of this. Now we will take a few minutes to do some test fitting here because it is kind of close between the hitch and the bumper. So, we use our bracket. We can mount it this way or we can mount it this way. And we can mount it just like this. It does stick out kinda far. So what we can do is we can just take this bracket and flip it around. And if we are installing it backwards, it actually recesses a little bit. It sits a little tighter against the hitch and it is not the only thing that is sticking out further than the hitch itself. 1:00

Alright, first we will install our bracket. Put the clamp over it and then we will run it through. The clamp is screwed down against it and then twist it. Now next we will go ahead and bolt on the bracket that came with the 4-pole and 7-pole adapter. Install the adapter itself. To take a few minutes out, we will go ahead and take up these wires to make them nice and neat, a little added protection. [Adapter 1:55] This 4-pole is going to plug into the factory 4-pole and then we will have a few extra wires. This will be used for a 12 volt hot lead, the black wire, if we needed to install that. We do not have to in this case. The blue wire is going to be for the brake output for the brake controller. Again, that is not going to be installed either. And what we have left over is the purple wire. That is usually ran to the reverse lights for reverse light lead, either on your trailer you may have a reverse lock out for the hydraulic brakes or just simply reverse lights on the back of a trailer. We are not going to use that one in this case either. That leaves us with the white wire, which is ground, right here. And we will run that to the frame member of the vehicle. So the remaining wires, we are just going to tidy them up for easy access at a later point in time, if needed. 2:49

Ok, before we plug these together, we are going to apply just a little bit of contact grease. It is going to help protect them over time. We are simply going to push those two together. And then what we will do, we will run a zip-tie. We are actually going to thread a zip-tie between these two wires and around the factory holder. We will actually put one on each side. We are going to attach our ground lead to this cross member right here. And to do that we are going to use a number 14 self taping screw. Alright, lets go ahead and just bundle up our wires now, kind of keep them safe and out of the way. And it looks like there is a little space between the hose clamp and the hitch so we can use that to our advantage. And run a little zip-tie and secure that. Alright and there you have it for part number 37185 from Hoppy and part number 118136 from Tow Ready. 4:06

Michael Z.


In this video you say This will be used for a 12 volt hot lead, the black wire, if we needed to install that. So, how would I install that black wire so I could charge the battery on my Tent Trailer while on the road. Thanks. Or do you recommend that?.

Etrailer Expert

Rachael H.


It is no problem to charge your battery on the tent trailer from the 7-way on your vehicle. To do this you will need to run a separate wire to the battery of your vehicle. I recommend using the complete kit # ETBC7 that includes the correct wire, connectors, and circuit breakers needed for a fully functional 7-way. I have included a help article that details the install of the # ETBC7. I have also included a video showing the installation of the # ETBC7 on an 09 Tacoma that shows routing the 12 Volt wire for your reference. This video also shows the installation of a brake controller and if you do not need that for your trailer disregard that portion of the video.

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