How To Determine If A Brake-Lite Relay Is Needed On My Flat Tow Setup

Updated 10/15/2025 | Published 08/10/2025

Question:

1 Do I need this part? 2 IF I need this part, do you have it for my setup? 3 Do I need to run something else to keep my battery from dying although it has never died, as I have only flat towed it once. My setup: 2003 Alfa See Ya pulling a 2024 2D, 4WD, MANUAL, Bronco with LEDs and auxiliary lights NOT the bronco lights as the rear stop, tail, and turning lights. I have a 7 way coming off the MH to a standard 4way flat, that I am about to upgrade to a 7 way to 7 way on the front of the towed. Any break it down like he was a 3 year oldinch would be appreciated.

asked by: Baihr

Expert Reply:

Hey Baihr,

In order to fully know if a brake-lite relay is needed for your setup there is a short questionar we recommend going through to determine if you need one. Since I do not have your vehicle in front of me it is a little difficult to tell. The questions are on the product page, but I will attach them here for you.

Is a Relay Required?

To determine if a brake light relay is needed to properly wire your vehicle to be towed, answer the following questions.

Are you using a supplemental braking system that depresses the brake pedal in your towed car?

No - You do not need a brake light relay.

Yes - You may need a brake light relay. Continue on to the next question.

Do the brake lights on your towed car illuminate while the engine is off?

No - You do not need a brake light relay.

Yes - You may need a brake light relay. Continue on to the next question.

Do your towed car's brake lights act as both the brake signals and the turn signals?

No - You may need a brake light relay. Continue on to the next question.

Yes - Your towed car has a combined lighting system. You will need a brake light relay to ensure proper activation of its signal lights.

Does your towed car have separate brake lights and turn signals?

No - Your towed car has a combined lighting system. You will need a brake light relay.

Yes - Your towed car has a separate lighting system. You may need a brake light relay. Continue on to the next question.

Are you wiring your vehicle with a six-diode kit or a TowDaddy custom wiring harness?

No - You will need a brake light relay to ensure proper activation of your towed car's signal lights.

Yes - You do not need a brake light relay.

Let me know your answers for that and we can figure out what you need for your setup.

expert reply by: Nick S

Nick S.

9/2/2025

Hey Baihr, Did you have a chance to go through the questionnaire to determine if you need a brake light relay for your setup? Let me know your answers, and we can figure out what you need to keep everything running smoothly. If you’re still looking for a solution, I’m happy to help.

Baihr

9/2/2025

@NickS I will be looking for a relay and CLEAR ,COMPETENT instructions on how to properly install it in my 2003 Alfa See Ya.

Nick S.

9/3/2025

@Baihr If you went through the questions and determined that you do need a brake-lite relay then what you will need is the Roadmaster # RM-88400, and I have attached the instructions for you.

Helpful Links

instructions.aspx?pn=rm-88400

Darcy

10/11/2025

Hi, I have the same question for the need of brake light relay; for most of the questions, the response would be yes, that I DO need one. However, the last question about the diodes; I am using 4 diodes for the rear lights (no amber, brake and signal only) so does that answer saying that I DO NOT need the relay, negate the previous answers saying that I do? A little confused. Thanks Darcy

Nick S.

10/13/2025

@Darcy With that many yes's I would say you need the relay. However, some vehicles are always unique. What kind of vehicle are you wanting to flat tow? I can get a better idea with the year, make and model, but I would say yes you would need one.

Darcy

10/13/2025

@NickS Hi, I want to tow a 2013 Mini Cooper base model.

Nick S.

10/15/2025

@Darcy It does look like you will need the brake lite relay # RM-88400 when flat towing that vehicle.