Hi all - I have installed a 4-flat trailer connector (Curt brand part #55316) and, then connected a 7-blade converter (Curt #57186), brake lights and running lights are all working properly. Electric brake and 12v aux wires run from the back and up into the engine bay, and the electric brake wire thru the firewall into the cab. I have the brake controller (Curt #51136) “quick connected” (plug-n-play) under the ashtray. It has power.

I understand all that is needed is to splice the elec brake wire to the blue wire coming out of the factory installed harness but I am struggling to figure out where along the blue wire in the cab to do that?
It looks to come from the fuse box (or PCM?) at the firewall and then up to the left of the brake pedal behind the dash and down into the factory harness.

Should the connection be made nearest the firewall? Or would it work to do it just before the blue wire enters the factory harness (which is then plugged into the trailer brake controller itself)

Any help very, very greatly appreciated!

 

I had to do this, on a 1994 F150.
The blue wire, under the dash, that connects to the brake controller, follow that into the firewall on the inside.
Then, in the engine bay, that same connection, is where there is probably no blue wire in the factory harness.

My truck had factory tow package, but for whatever reason was missing that blue wired in the harness.
I had spare pins, from a different plug, and wired it with a pin, and into the factory plug/harness.

The new blue wire is then connected in the engine bay, in the factory plug.

Hope that makes sense. I can take pictures and have wiring diagrams if needed.

 

Lifesaver! Thanks so much for the info - If you have time, a couple pictures (maybe one inside the cab and one in the engine bay where you made the connection) would be a Godsend and very much appreciated

 

Will do, hopefully tonight, if not will be friday.

 

 

Kinda useless wire diagrams. I see the blue wire, but it does not show the plug or connection point, other than stating its for electric brakes.

 

This is from a 1997 F150. All of this information is on the Charm website.https://charm.li/Ford/

 

^^^^^ not bad, but lets use the 1994 Ford Service manual schematics:

It's wire #43 Dark Blue(DB) goes from the brake controller plug connection/component (C210) to the firewall connection/component(C205).
At C205 the DB wire is located at pin #2, which then goes all the way to the back of the truck.

If your lucky, you have that. I was not so lucky, but ended up pulling the whole rear wire harness from a truck in the junk yard and installed it to be like factory.

Electronic Brake Controller

Firewall C205

Brake Controller C210

 

Linking to another post, @subford explains and has pictures of the exact issue:
https://www.ford-trucks.com/forums/1...l#post19165291

 

Thanks to all for the input and info - Using a tap wire connector I connected the electric brake wire running from the vehicle-side 7-blade kit into the cab to the light green wire (brake on/off switch) at the factory plug (before it heads into to the brake controller plug)

This seems in keeping with the 7-blade kit instructions and the electric trailer brakes seem to be engaging and disengaging properly. I noticed in the top of two diagrams above that the light green at that point seems to be able to go to the electric brake controller?

Just wondering if this presents any potential problems (ex. with the functioning of the brake on/off etc.?) In other words; is this the viable option it seems to be, or does it need to be wired to the blue wire?

 

That is incorrect, the light green wire is your brake on/off, input into the controller.
The controller then outputs to the blue wire, using power from the red wire.

You have connected your brake switch on/off to your trailer electric brakes. Incorrect.
You need to connect the blue wire(output) to your trailer electric brakes.

Yes this will create problems. You will overload the factory truck brake circuit.
No this is not a viable option.

You must wire the blue wire, as that is the output to your trailer electric brakes.

 

Thanks for the speedy reply and confirmation - will rewire immediately

 

good information, im glad you found the specific connector stuff. my sources were kinda dry but were what i could find.

the expalnation is also good because someone c ould easily see why the brake wire should work but then remembering how electric trailer brakes work one can see how its going to quickly be overcame

 

In addition to thanking everyone again, I wanted to follow up to leave a note on what I ended up with (in case someone with the same or a very similar setup is looking at this in the future).

The electric trailer brake wire (included with the 4-pin to 7-blade converter (Curt #57186 )) runs from the rear of the truck along the driver's side frame rail up into the engine bay and on into the cab through a factory hole (removed rubber grommet) located to the driver's side of the brake booster. From there the the wire runs to the factory plug under the ashtray and is connected via a t-tap connector to the dark-blue trailer-brake wire on the truck-side of the 'quick-plug'. The quick-plug connects via a wiring harness (Curt #51323) to the trailer-brake controller.

The reasoning behind my initial incorrect wiring (to the light green 'brake on/off switch' wire) at the point of the factory plug was that the dark blue wire at that location was not showing a signal on a test light when brakes were depressed whereas the light green, of course, did - but this is because I foolishly did not have the trailer brake controller connected when I was using the test light on the truck-side of the quick-plug!
The key for the solution to my misunderstanding was this:
Once the trailer brake controller was connected, the dark-blue wire received the necessary output and then lit up the test light properly when the brakes were depressed, and the trailer brake controller and trailer brakes worked properly.