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Old 03-21-2013, 11:17 AM   #1
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Location: Wylie, TX
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2009 F150 Trailer Brake Question

I just realized today that apparently there are some components to my electric trailer towing system that weren't installed at the factory. I found the bag and it contains a trailer tow wiring harness, trailer tow battery charge relay, and a trailer tow battery charge fuse.

I assume I need to install the relay and the fuse in order for my truck to charge the TT battery while I'm travelling.

My question is, what is the harness for? My running lights, brake lights, turn signals, and trailer brakes all currently function properly.

Is the harness part of the charging system also? It has 4 wires coming out labelled as follows:

Blue - to trailer electric brakes
Green - stop lamp
Red - feed wire from battery
White - ground

I'm new to all this, and learning something everyday. So, thanks in advance for the education!

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Old 03-21-2013, 05:36 PM   #2
Join Date: Dec 2008
Location: Hartford, AL
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No I think your harness is a ford pigtail to install a brake controller. It's not required for the charging the tt.

2007 Chevy 2500 HD 6.6
2012 Sabre 31RETS
(LA) Lower Alabama
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Old 03-21-2013, 05:42 PM   #3
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Location: Iowa
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Yes, the harness was to hook into the factory wiring under the dash for trailer brake controller.

Yes, you will need to install relay for charging the tt battery whilst hooked up and towing.
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Old 03-21-2013, 05:46 PM   #4
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Location: Eastern PA
Posts: 248
I agree with H20ski, my Dad has an 07 and he had a similar thing. Ford leaves the connector under the dash above the control pedals. When you buy a brake controller, you would plug what you have into the connector under the dash and then connect the bare ends to the corresponding function on the brake controller's harness.

However, to make it even easier most brake controller manufacturer's have harnesses that go direct from their controller to each manufacturer's connection. I'd keep what you have for spare parts.

Have fun camping!
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Old 03-22-2013, 08:36 AM   #5
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Thanks everyone!

The weird thing is my truck came with a brake controller already mounted on the dash. I guess they just throw the whole pack of components in there anyway.
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Old 03-22-2013, 08:51 AM   #6
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Location: Chelsea, Alabama
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I had ford to install a in dash controller when I bought my 2010.I to found a bag with all that you have mention.After doing some checking the relay and fuses were already installed.I guess they came with the controller.
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Old 03-22-2013, 10:05 AM   #7
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Location: NW AR
Posts: 151
The fuse block for the relay and the fuse are under the hood right in front at the top of the radiator. Ford does not install these even if you have a brake controller installed from the factory and there is no good reason why. I had a controller installed at the dealer. They still didn't install the fuse or relay and didn't even tell me that I had to do it myself. I had a friend who also bought an F-150 after he saw mine and he was treated the same way. Neither one of us will be back to that dealer for any reason.


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