How to Find COLD Side of Brake Light Switch for Hardwiring Brake Controller

Question

Question:

How do i get a hot wire off of brake light switch

asked by: Dave

0

Expert Reply:

When you are hardwiring a trailer brake controller like the Prodigy P2 # 90885 the red wire connection that provides the triggering signal to the controller should be made to the wire on the COLD SIDE of the brake light switch circuit. This is the wire that carries 12V power ONLY when you press the brake pedal and at no other time. Please refer to the linked photo and article for more details.

If you were to connect the Prodigy to the HOT side wire then the controller would constantly generate brake output to the trailer and you would not get too far.

Applying a circuit tester like # PTW2992 is the best method for finding the correct wire at the brake light switch.

expert reply by: Adam R

0

click to enlarge

Dan S.

3/30/2020

Tekonsha says not to connect to a wire that goes to ground when the brake pedal is not depressed. I have 2 wires in my brake position switch that get 12v when brake pedal is pushed, but they both go to ground when it is released.Any thoughts?

Reply

Chris R.

4/1/2020

You might be able to access the cold side of the brake light switch somewhere else on the vehicle (you're right not to use either of the two wires you found). If you can tell me what model vehicle you have I'd be happy to provide a more specific answer. Another option is to add a Brake Light Switch - which again are vehicle specific.

Reply

Frank G.

6/29/2022

@ChrisR I have the same problem finding a brake voltage that does not go to ground when pedal is not pressed. I have a 2011 Ford Ranger a d I’m pulling my hair out on this one. Where else could brake 12v be found in the cab ?

Reply

David B.

7/5/2022

Maybe this will help it is our video of a P2 install on a 2011 Ranger. https://www.youtube.com/watch?v=_qBVufIGQHI

Reply

See All (7) Replies to Dan S. ∨

Dan S.

4/1/2020

2016 Thor ACE motorhome built on F53 chassis.Every one Ive talked to and everything Ive read online insists that I have a plug and play connector in the dashboard. However, after removing the dash and searching through it, theres nothing even resembling one. There are several unconnected wires, but they have labels for PTO and blower motors. Not sure what you mean by Brake Light Switch, do you mean the switch thats activated by the pedal? Those are the wires Im referring to. There are 4: one is constant 12v, one is constant ground, the other two are the ones mentioned above. Where else on the vehicle could I access the cold side?

Reply

Chris R.

4/1/2020

Thanks for the info! It's really odd that it doesn't have a factory port - take a look at the linked answer below that actually shows a picture of its typical location so you can check one last time. If you still aren't able to find it, your best option is to use the Stop Light Switch Kit # RM-751000, which basically lets you wire in your own brake light switch to use for the controller.

Helpful Links

question-311209.html

Reply

Adrian S.

5/30/2025

I have 2003 gmc trying to wire and connect a Tekonsha red wire to cold side of brake switch what wire is the correct one

Reply

Robin H.

5/31/2025

@AdrianS a 2003 GMC what? I might be able to find the wire color if Roadmaster lists it but I will need to know the model of your vehicle. If they don't have the wire color you need to follow the instructions above and test to find it.

Reply

Answer 1

Normally you can find the brake light switch under the dashboard at the top of the brake pedal. There could be a number of wires attached to the switch so you can use a tester like part #PTW2993 to test the wires. Since the auto manufacturers can use…

view full answer...

Answer 2

To add a brake controller to your 2023 Ford Maverick I recommend installing the Tekonsha OEM Replacement Vehicle Wiring Harness w Brake Controller Adapter #TK95VR to get the wiring and then the Redarc Tow-Pro Elite Brake Controller for Tekonsha…

view full answer...

Answer 3

The Furrion #FMCM15SS is a great appliance that will meet your needs. I researched the dimensions of your original Dometic and discovered they are 29 15/16" wide x 16 7/16" tall x 15 3/8" deep. The Furrion I'm recommending will fit…

view full answer...

Answer 4

Hello Travis, thanks for reaching out. For your 2025 Kia Telluride EX X Line I recommend the etrailer Class 3 Hitch #e45ZR. This has a 2" receiver, and features the matte black coating you are looking for. We have found the matte black coating…

view full answer...

Answer 5

I checked with Demco and according to them, the Demco Classic Base Plate Kit #DM9518072 is a fit for all 2000 Jeep Grand Cherokees. I have added a photo from the instructions which actually shows these base plates installed on a Grand Cherokee with…

view full answer...

Answer 6

A 4-Way trailer connector has the basic lighting functions only; running lights, left turn signal and brake lights, right turn signal and brake lights, and ground. A 7-Way has these functions and a 12 volt circuit, a circuit for electric trailer…

view full answer...

Answer 7

I contacted the manufacturer and the Tekonsha Prodigy RF Wireless Trailer Brake Controller, Item #TK94FR, will work with your 2017 Toyota RAV4 Hybrid. When it comes to wiring, you do not have to connect to the brake wires but will need to connect to…

view full answer...

Answer 8

Toyota didn't offer a factory 7-way option for the 2006 Tacoma, so your 7-way was either aftermarket or dealer-installed. I'm assuming that your 7-way is already tapped into the lighting circuits. Look under the dash for a coiled up blue…

view full answer...

Answer 9

Hey Kevin, if you were looking for an excuse to upgrade to a newer braking system like the Blue Ox Patriot part #BLU37TR now would be a great time...but typically if the Roadmaster Even Brake Portable Supplemental Braking System #RM-9400 is having a…

view full answer...

Answer 10

We have 2 different wiring harnesses that tee in behind your 2018 Toyota Tacoma tail lights and provide trailer functions: - Curt T-Connector #C56349 - Tekonsha OEM Replacement Vehicle Wiring Harness w Brake Controller Adapter #22117 I wasn't…

view full answer...

Answer 11

Thanks for reaching out! Since you have the 4951KS model MaxxFan roof vent you'll need the Replacement Printed Circuit Board for MaxxAir MaxxFan Plus Roof Vents #MA10A04751KS. The circuit board might look slightly different as far as the pieces…

view full answer...

Answer 12

It looks like you've got everything you need, except for a brake controller. The Curt #C51180 Echo Wireless Brake Controller would be very effective, with your vehicle being already pre-wired, the install would be plug and play. The only knock I…

view full answer...

How to Find COLD Side of Brake Light Switch for Hardwiring Brake Controller

Product Page this Question was Asked From

Featured Help Information

Instructions

Miscellaneous Media

Continue Researching