Installation Instructions for Roadmaster Brake Lite Relay and Brakemaster 9000  

Question:

Helpful Expert Reply:

There are two methods of installation for the Roadmaster Brake Lite Relay part # RM-88400 that you referenced, open and closed.

Most towed cars require the normally open installation method. Ford and Lincoln models with neutral tow kits and most automobiles that have a push-button start function will require the normally closed installation. Check out the diagram that details the installation.

Remove the blue wire from the kit. This wire is not needed for normally open applications.
Locate the brake-light-switch wire in your towed car.
Remove the brake light fuse.
Cut the brake light wire a few inches away from the "cold" side of the brake light switch.
Attach the relay to the wiring for the RV braking monitor. The diagram above shows where the green wire attaches the relay to either a Roadmaster Even Brake or BrakeMaster system.
Connect the black wire of the relay to the brake light wire near the brake light itself using the included blue butt connector.
Connect the red wire to the "hot" side of any fuse that is powered only when your ignition is on. Use the included spade connector and fuse tap.
Ground the white wire to your towed vehicle's frame.
Secure the relay with the included wire ties.


If you have a Ford or Lincoln that has a neutral tow kit or if your car has a push-button start feature that will not start the engine when the brake fuse is removed, then you need to perform a normally closed installation. Be sure to follow the instructions included with your relay kit for a more detailed process. Normally closed operations may require additional connectors and length of wire that are not included with this kit. Attached diagram for this as well.

Remove the green wire from the kit. If you are using a Roadmaster Even Brake supplemental braking system, set this wire aside to use later.
Locate the brake-light-switch wire in your towed car.
Remove the brake light fuse.
Cut the brake light wire a few inches away from the "cold" side of the brake light switch.
Attach the relay to the wiring for the RV braking monitor. The diagram above shows where the blue wire attaches the relay to either a Roadmaster Even Brake or BrakeMaster system. The green wire may be needed here.
Connect the black wire of the relay to the brake light wire near the brake light itself using the included blue butt connector.
Use a voltmeter to identify the wire in your aftermarket light harness that is conducting the tail light signal. Typically, this is a brown wire.
Using a 16 - 14 gauge butt connector (sold separately), attach a section of 14-gauge wire (sold separately) to the end of the red wire. Trim the new 14-gauge wire and connect it to your aftermarket wiring harness.
Start your engine and turn on your headlights. Test the tail light wire with a voltmeter. If your voltmeter doesn't register any voltage, move on to step 10. If 12V DC registers, you will need to install a single diode (RM-790; sold separately).
Ground the white wire to your towed car's frame.
Secure the relay with the included wire ties.

I noticed you also mentioned the Brakemaster 9000, I attached installation instructions for this product as well to the right under the helpful link heading.

expert reply by: Jameson C

1

click to enlarge

click to enlarge