Where Does The Red Wire Install to On the Roadmaster Brake-Lite Relay Kit 2007 Hummer H3

Updated 03/04/2026 | Published 02/21/2026

Products Featured in This Question

Roadmaster Brake-Lite Relay Kit for Towed Vehicles

(738)

$43.69

Question:

I am installing a Roadmaster brake light relay RM 88400 on a 2019 f 150. Does the red wire connect to the brown wire from the motorhome? Thanks

asked by: Jerry W

Expert Reply:

Hey, Jerry.

Since your Hummer is a 2007, I’m going to assume it has a key-start ignition. For that setup, the red wire on the Roadmaster Brake-Lite Relay Kit, part # RM-88400, will connect to the fuse tap. I’ve included the steps for that portion of the install below, along with the diagram for reference.

- Insert the fuse you just removed into the slot closest to the fuse blades (Figure 2).
- Then insert the fuse tap into the empty slot in the fuse panel (Figure 1).
- Using the attached blue butt connector, connect the red wire from the Brake-Lite Relay to the wire from the fuse tap (Figure 1).

Is this your first time getting into flat towing, or are you just switching up the vehicle you’re towing?

expert reply by: Gwendolyn Y

Diagram
(click to enlarge)

Roger M.

3/4/2026

everything installed and works as it's supposed to. I ran my wires through the firewall through a factory grommet, then along the left footwear and followed the factory harness under the sill guard and over the fenderwell to behind the left tail light module. Much cleaner than through frame rail. remaining wiring runs along rear frame structure inside wire loom tied down with zip ties.. The factory got the color code wiring for power backwards, power is power, everything works.