See What Fits Your Vehicle
customer service | view cart  View Cart

Tow Bar Braking Systems > Brake Light Relay > Roadmaster

Roadmaster Brake-Lite Relay Kit for Towed Vehicles

Roadmaster Tow Bar Braking Systems

Rating: ratingratingratingratingrating
3 reviews


Code:   RM-88400

Retail:$35.39

Price:$27.33

Shipping Weight: 4 pounds

Shipping Special
Quantity: 




Roadmaster Tow Bar Braking Systems - RM-88400

Relay works with your tow bar wiring system to ensure that your towed vehicle's turn signal lights flash in tandem with your RV's lights.

Features:

  • Keeps your towed car's brake signal from overriding the turn signal sent by your RV
    • Allows signal lights on towed car to flash in tandem with RV lights even when vehicle's brake pedal is depressed
  • Required on towed cars with combined lighting if you are using a supplemental braking system
    • Needed on applications with separate lighting if towed car is wired using a TrailerMate wiring harness or a 4-diode kit (instead of a 6-diode kit)
  • Does not interfere with towed car's electrical system
  • Activates automatically when RV running lights are turned on
  • Includes all necessary components for standard installation
    • May require additional connectors and length of wire for certain applications


The purpose of a brake light relay kit is to prevent your towed car's brake signal from overriding the turn signal that comes from your RV. When your towed vehicle is properly wired and connected to your RV, its indicator lights will illuminate as you engage the turn signals in your RV. However, if you have only a four-diode system in place, the turn signal will be overridden by your towed car's brake signal as soon as your supplemental braking system presses the towed car's brake pedal. As a result, drivers behind you know only that you're slowing down and not that you are turning.


Installing a brake light relay in your towed vehicle fixes this problem by ensuring that your car's brake signal does not override the RV's turn signal. Therefore, your towed car's lights will function in accordance with your RV at all times.


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.


Installation of the Roadmaster Brake-Lite Relay

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.


Normally Open

The diagram and steps shown below demonstrate the installation for normally open applications. Be sure to follow the instructions included with your relay kit for a more detailed process.


Standard Normally Open Installation for Roadmaster Brake-Lite Relay
  1. Remove the blue wire from the kit. This wire is not needed for normally open applications.
  2. Locate the brake-light-switch wire in your towed car.
  3. Remove the brake light fuse.
  4. Cut the brake light wire a few inches away from the "cold" side of the brake light switch.
  5. 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.
  6. Connect the black wire of the relay to the brake light wire near the brake light itself using the included blue butt connector.
  7. 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.
  8. Ground the white wire to your towed vehicle's frame.
  9. Secure the relay with the included wire ties.

Normally Closed

The diagram and steps shown below demonstrate the installation for normally closed applications. 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.


Normally Closed Installation for Roadmaster Brake-Lite Relay
  1. 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.
  2. Locate the brake-light-switch wire in your towed car.
  3. Remove the brake light fuse.
  4. Cut the brake light wire a few inches away from the "cold" side of the brake light switch.
  5. 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.
  6. Connect the black wire of the relay to the brake light wire near the brake light itself using the included blue butt connector.
  7. 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.
  8. 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.
  9. 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).
  10. Ground the white wire to your towed car's frame.
  11. Secure the relay with the included wire ties.


88400 Road Master Brake Light Relay





Video of Roadmaster Brake-Lite Relay Kit for Towed Vehicles


Videos are provided as a guide only. Refer to manufacturer
installation instructions and specs for complete information.

Video install brake system 2001 chevrolet tahoe rm 8700
Roadmaster InvisiBrake Supplemental Braking System Installation - 2001 Chevrolet Tahoe

Video Transcript for Roadmaster InvisiBrake Supplemental Braking System Installation - 2001 Chevrolet Tahoe

All right. Today, on this 2001 Chevrolet Tahoe, we're going to install part number RM-8700 from Road Master, and this is a brake kit. Okay. To start off the install, we remove the threshold and also the kick plate by the compartment brake. We lift up the trim panels in the back. We're going to route our cylinder next to the driver seat, and we will attach it later on to the metal bracket that's near a console.

We will take out cable and were going to route it underneath our plastic here.Now, were going to route it up and over the support underneath the dash and over the interior air docks, and we route it down through here along for pulley. Now we did take our pulley loose by these two pins here and took it apart to make it easier to thread through. Then we just reassembled it. Now, when we attach our pulley, weve got to find a spot so that our cable will go around the pulley and reach to our brake pedal.Over here, were going to cut off the installations. We can mount our pulley straight to the firewall.

Now, we can go ahead and start installing our clamp that goes through the brake pedal. What you want to aim for is this being tight with just a little bit of playing it about the size of this ball in the end here, a quarter inch. Now, we all now have planned out for sure who's going to fasten it down.All right. Now, we'll go ahead and mount our cable to the firewall. All right.

We're going to go ahead and add zip tie to the upright where our cable is, secure it. Were going to leave this part alone for now. Let's go to the cylinder and we'll go ahead and install our clamp for that. All right. Now, our cylinder is going to mount to this bracket right here, and we use a clamp that will hold it in place.Before we do that, we have to our air line right here.

Okay. We're going to do our best to route our lines under these rails here so it won't slide back and cut the line. Were going to take a line. We're going to run it underneath our carpet. Well take our other new air line and all you've got to do is push it right into the fitting. You just push it in as far as you can. You have to tug back and inaudible 00:02:31 locks in.Okay. Now, let's go continue over our small line here. We're going to go underneath the carpet, and then we're going to wrap this back up under our seat where the InvisiBrake compressor is hiding. Route it under the jack tools. Okay. Were just going to push it right in, just like the other fitting until it stops, and then pull back, and its installed.Okay. Now, we'll go ahead and run our next line which will be a vacuum line, which will come from this port here. Were going to run it all the way up to the front of the vehicle. To attach our nylon vacuum line to the InvisiBrake we're going to slide on a piece, a quarter inch of rubber line, and route that underneath the jack tools as well. That's going to push right on. That's really it.Now, were going to continue on running up to the front. Were going to follow the same path as our air line, but were going to go up to the firewall. Now, normally we would have to draw a hole through the firewall to get to the outside so you can get to the vacuum line from the brake booster. We got lucky at this point that this vehicle already has a hole drilled through the frame, so were going to use it.Make sure the line is underneath all the panels. We'll go underneath the hood and make our connection. Here's our vacuum line. Route it to make sure that they're away from anything hot or moving. Now, were going to make some connections through a vacuum line. First, were going to add the T right here so we'll make a cut in our line or a T the way the small section to connect the check valve with the T.When we install our check valve, we want to make sure the red is always going towards the engine. Now, our kit does come with a small section line. We can actually use that as part of our install. We'll go ahead and slip that on. We'll take the other half of our line. We'll probably trim it up just a little bit as well and install it.All right. To connect our nylon vacuum line, again, we're going to use a small piece of quarter-inch tubing. Now, were going to take our wires with the black and red, and the black and white. We can go ahead and hook these up to InvisiBrake. The black wire will go out front of the vehicle to the breakaway kit, and the red and black wires will go to the battery and powering ground.Basically, we'll run the wire same way we did with the vacuum line, and well go out a different point of a vehicle. This grommet for the parking brake, were going to use that to go outside. Lets cut a slit in it and then run our cables through it. We'll then go ahead and burn our black and red wires through.We'll go ahead and take our wires. Well pull out our slack. Okay. We'll go ahead and pull our wires up. Now, well take our red and black wire. We'll leave it by the battery. Then our black wire, these two pulled in, we'll run that down to the bumper. Okay. All right. Now we can go ahead and start connecting our black and red wires.Our red wire will go to the positive terminal and our black wire will go to ground, and we'll run that to the body. For our positive terminal on the battery, were going to be using the brass bolt battery extender from Deka. All right. This basically replaces the post that's in the battery. Basically, we had to pry out this bolt as best as we can, and we'll go ahead and replace it with this part.The big terminal will run to the positive side. Okay, and then we'll go ahead and reinstall it to the battery. We will trim up our wires, and we'll go ahead and add our ring terminals. This section is steel. It's double-layered, so were actually going to use a longer screw that what is provided in the kit to go through both layers. Before we add a red wire to our battery terminal, let's strip the wire back.We'll inaudible 00:07:31 one half of our fuse holder and we crimp right here. We'll install our fuse, put the other half are harness on top of it, and just push this together. Okay, we'll now go ahead and add this to our battery terminal. We're going to go ahead and install our breakaway switch.Now, there isn't really not much to attach to, but not covered up, but were going to put in this location back here. There's a piece of metal that we can attach to that's going vertical, so were going to take this part of a bracket and were just going to put a 90 degree turn on it. Okay. After the breakaway switch is mounted, we'll go ahead and connect the two halves together. We're just going to zip tie our extra out of the way.Quick test by pulling out on the breakaway switch. Now, were going to take our wire harness with the four wires and well plug that into back of InvisiBrake and, one more time, we'll take these wires and follow the same route as our red and black wires did. We'll go ahead and follow the same route as before going up to the same grommet as our red and black wires.Now, these four wires, we're going to hook up to our wire harness that are used for the towing lines that's behind the RV. Right now, were going to take our purple wire and we're going to route it towards the back of the vehicle. Were going to hook up before our aftermarket towing harness.All right. Now, this is a wire we're just adding in, and this is our existing aftermarket wire harness that's previously installed. We've got a color code for this wiring. Green is right turn. Yellow is left turn. Brown is inaudible 00:09:44 lights, and white is ground. That's the same code that's commonly used on towing harnesses.In this case, were just going to match everything color to color and use a block connector to inaudible 00:09:54 everything together. Then, we'll go ahead and install everything back into the frame. Now, to connect all three of the wires together, to access wire and the third wire, were just going to use a block connector.Okay. We've got our ground done. Lets go and repeat the same process for the remaining wires. Once you inaudible 00:10:40 along a specific spot to mount our box, we'll go ahead and make a cottony carpet so we can get down some sheet metal below. Well run some inaudible 00:10:49 to screws to attach to.Now, we have most of the components installed and we can go ahead and reinstall the interior panels and carpeting in the back of the truck. We're just about done for install for inside of the vehicle. We need to add one more cable and this is for a monitoring system that goes between RV and the towed vehicle.This simple plug right here, we're going to push to the same grommet as we used for our breakaway switch and we're going to follow exact same route and come out down by the wiring connector at the front of the vehicle. Okay. We'll run our wire up by a four-pole connector here. All right. This is the other end of the wire right here, and we're simply going to wrap this up towards the closer side of the brake switch.Because this truck has a combined wiring system, we need to install a brake light relay kit. Because both of the RV monitor cable the brake light relay are connected to the cold side of brake pedal switch, we can install them together. This relay is required on towed vehicles that have a two-wire system when using a supplemental brake system.To install the kits, weve got to find out which wire is the cold side of the brake switch, so that means when we hit our brake pedal, the wire will get hot, and when its not, it will be the cold side. Okay. We test this first light where this white wire goes into, so that will be a cold side of our switch.All right. To protect the circuit we're working on, were going to remove the fuse. All right. Now, we're going to make a connection to the brake wire. That's the cold side of the switch. Were going to cut it in half. For our relay kit, were going to attach the green wire and also the RV mounter black wire.We're going to combine these two to one-half of a block connector and connect the other half to the white wire. Okay. Now, our black wire, were going to connect a blue block connector to it. Then this will get connected to the other half of the white wire that we cut. Okay. Now, we're going to take our red wire. We're going to attach this using a fuse tap, going to the fuse panel.Now, we can use any fuse we want as long as it has power going to it when the key is on the on position, which will block connector to inner wire and has a fuse to tap and a separate slot for a factory fuse and for our new circuit.This with part number F2526. We're going to make our connection, and then we'll run our wire up to the fuse panel. We've got our fuse for our factory accessory and another inaudible 00:13:25 fuse for our relay kit. Were going to leave this unplugged until were finished with our installation.All right. Next, we'll go ahead and deal with our white wire, and we'll ground this to the body. We will install our fuse into the fuse holder. With our connections made, we'll take our fuse tap, install back into the fuse block, and then we can go ahead and zip tie the relay and the wire safely out of the way.We're going to start running the cable for the motor home. We're with the female in here on a 50-foot cord. Were going to tie this off by the trailer connector, and then run this up to the dashboard. All right. To the other side of our black wire, and we'll attach that to the body ground.Now, we can connect our harnesses together. All right, we'll go ahead and test the system per reinstructions. Okay, with that, that will finish it for our install of part number RM-8700 from Road Master, and this is a brake kit, on this 2001 Chevrolet Tahoe.


Customers compare RM-88400 to these similar products





Customers Who Purchased This Tow Bar Braking Systems Also Bought...






Customer Reviews

Roadmaster Brake-Lite Relay Kit for Towed Vehicles - RM-88400

Average Customer Rating:  ratingratingratingratingrating5.0 out of 5 stars   (3 Customer Reviews)




- RM-88400

ratingratingratingratingrating by: Mike V.03/23/2013

Is this review helpful?


Pretty easy to install with good directions. Straight-forward, works as advertised!72100

comment on this review


- RM-88400

ratingratingratingratingrating by: Ronald P12/05/2012

Is this review helpful?


Very fast delivery, everything looks good. Think installation will be pretty easy with very good instructions included in this kit and basic ally a plug in set up! Highly recommend Etrailer very helpful, friendly, and quick service.60783

comment on this review


- RM-88400

ratingratingratingratingrating by: Rick B03/21/2011

Is this review helpful?


Product was at a good price. It was shipped quickly and I received it promptly. Etrailer is a great company to order from and I highly recommend them. That said, the brake light relay performs exactly as it is supposed to. I am well pleased!10000

comment on this review


Ask the Experts about this Roadmaster Tow Bar Braking Systems


  • Does a 2008 Chevy HHR Need a Brake Light Relay to be Flat Towed
  • On the 2008 Chevy HHR, Roadmaster recommends installing a 12 volt outlet, # RM-9332, and a brake switch kit, # RM-751428. Because your HHR has a combined brake and turn signal circuit, a brake light relay, # RM-88400, is not needed. From the information I have, you will need to pull a fuse or fuses. Consult the vehicle owners manual to determine any additional specific information on fuses that need to be pulled.
    view full answer...


Info for this part was:


Written by:
Lindsey

Edited by:
Leah

Test fit by:
Patrick

Video by:
Zack

At etrailer.com we provide the best information available about the products we sell. We take the quality of our information seriously so that you can get the right part the first time.





Subscribe to email newsletter

Email  

privacy - we don't send unsolicited email




etrailer.com reviews etrailer.com reviews

All images, layout and content copyright etrailer.com