Brake Controller Wiring - Brake Signal Tap Point

[Elecmuso]

I have a 2008 Outback to which I am about to install a brake controller. I need to tap into the brake light wire (which is an input into the brake controller). Can someone help me locate that wire and the best place to make the tap?

Also would be helpful to know the best place to route the controller power cables through the firewall.

Cheers

Greg

[Elecmuso]

If you happen to have a brake controller installed in your Outback could you just have a look around the brake pedal region?

Would be much appreciated.

[plain OM]

I don't have a brake controller. However, I've attached relevant parts of the wiring diagram.

As seen on the Cruise Control diagram, the brake switch has four terminals, pins 1 and 4 are used by the cruise control, and pins 2 and 3 are used for the stop lights. (See also the stop light diagram that shows this.)

Note that the stop lights are turned on by switching the 12 V supply to the lights. If the controller input is supposed to be the switched 12 V (i.e., 12 V when the brake is pressed, 0 when it's not), then pin 3, (BrW) is probably the wire to connect to.

Hope this helps -- let us know.

[Elecmuso]

Thanks - yes that should be very helpful. The normally open 12V contact should be the one as you suggested.
Do you happen to know a good way to get through the firewall?
Cheers
Greg

[plain OM]

Not offhand, but there should be some rubber grommets in the area that would allow for a wire to be passed through. That's the usual way.

[John E Davies]

On my 07 XT, I recently ran some wires for driving lights - I used the fat rubber grommet below the brake master cylinder. You can pop it out with a flat bladed screwdriver, drill or punch a hole, thread the wires through, then reinstall the grommet.

Easy, easy, EASY! Especially compared to some cars I have done.

What controller are you using? Are you going to run a battery charge wire too? Where are you going to run the wires inside the car?

I need to install one someday.....

John Davies
Spokane WA USA

[Elecmuso]

Just tapped the wire as per schematics provided by Plain_OM. Tested the signal and exactly as expected - pedal down, 12V out. Cheers!

Thanks John for the firewall info. I'll have a look in a minute.

I'm installing a Tekonsha Primus IQ.

Not sure what you mean regarding the battery charge wire. The contoller has an output wire to power the trailer brakes. Plus an input wire from the car battery to provide power. Plus an input wire from the brake pedal switch (just sorted this one).

Good question re: running the wires inside the car - haven't got there yet but I will let you know when I do!

[Elecmuso]

John

Found what I think you were referrng to. Actually slightly to the RHS of the master cylinder (facing the front of the car) and diamond in shape. About 1.5 inches high, 3 inches wide.

Cheers

Greg

[John E Davies]

Originally Posted by Elecmuso

Not sure what you mean regarding the battery charge wire. The contoller has an output wire to power the trailer brakes. Plus an input wire from the car battery to provide power. Plus an input wire from the brake pedal switch (just sorted this one).

Besides the brake controller wire, many trailers also require a circuit to charge the "house" battery. Sure, most trailers that you can haul behind an OB don't have one, but some small pop-ups do. It is a lot easier to run an extra 12 AWG (red or black) wire now and not need it, than to have to do it all over again in a few years.

At the very least, consider stringing that extra wire through the cabin and coil up the excess at each end and stow it securely. You don't have to hook it up to your battery or to the trailer connector, but I guarantee that if you ever do need it, you will be VERY happy you installed it way back when.....

Trailer Wiring Diagrams | etrailer.com

John Davies
Spokane WA USA

[Elecmuso]

Thanks John

Installation is nearly done (OK I may have to add that extra wire you suggested!) Only problem I'm having is getting that bl**dy grommet back in! I can get the centre large round middle plug through but the 2 small 'rubber studs' adjacent the centre plug are very diffcult to get through. Any tricks?

Greg