Universal Stop Light Switch for Brake Light Relay for 2023 Ford F-150
Updated 11/03/2025 | Published 02/10/2025
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Question:
I have a 2023 F-150 set up to flat tow. I have already installed the Roadmaster Direct Connect Base Plate Kit Part Number: RM38VR. I have also installed the Roadmaster Smart Diode Kit for Variable Voltage Incandescent Tail Lights Part Number: RO94FR. For a supplemental braking system, I will be using the portable RVI Brake 3. My truck has push-button start and neutral tow mode. According to my research, I need to install the Brake-Lite Relay Kit RM-88400 so that towed vehicle brake and turn signal lights work correctly. It also appears that in order to install Brake Light Relay, I need to use the Binch instructions for a normally closedinch application. I cant find any install videos for F150 newer than 2018, so Im having to use the Fitmasterinch chart from Roadmasters website to confirm details. My two questions are these. First, it appears that I cant install the brake lite relay using the normal method because the new truck brake switch wiring is too small to splice into... does this mean I have to somehow incorporate the Roadmaster Brake Light Switch 751506 into the installation of the Brake Lite Relay? If so, I cant find any wiring diagram on how to use the Relay switch in conjunction with the brake light switch. Second Question - for the install of the Brake Light Relay using the Binch instructions for push button start Ford blue wire used, not green wire - it says I have to attach red wire to the brown taillight wire coming from the motorhome. This requires that the motorhome tail lights be turned on all the time in order for the brake light relay to work. I dont like this, as Im bound to forget to turn taillights on during daytime. Could I not make the brake light relay work the same way by attaching the red wire to the battery charge line coming from the motorhome instead of the tail light wire? Seems like it should work the same, as charge line will also delivery power to towed vehicle even when tail lights are off.
asked by: John S
Expert Reply:
Hey John, on a vehicle like your 2023 Ford F-150 where the stoplight circuit is really hard to access or splice into I would recommend using a universal stop light switch like the Roadmaster part # RM-751000 with the brake light relay part # RM-88400. This will give you the stoplight circuit you are in need of and allow you to avoid any more wiring headaches.
Product Page this Question was Asked From
Roadmaster Brake-Lite Relay Kit for Towed Vehicles
- Flat Tow Brake System
- Brake Light Relay
- Roadmaster
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on Flat Tow Brake System
Jameson C.
10/30/2025
Hey John, how did things go pairing the universal stop light switch with the brake light relay on your F-150? Your results could really help others working through the same wiring challenge on newer trucks.