I recently had to hook a brake controller to my RV and used several threads here to piece together some of the info I needed. Monaco provided some info and the rest I figured out. I wanted the info I found documented somewhere in case someone else ever needs to do what I did.
2005 Holiday Rambler 40PDQ on Roadmaster chassis. Called Monaco and they state there is no wiring harness for a 2005 model (2004 chassis). Wiring harnesses were added on the 2005 chassis (probably 2006 models).
Confirmed that the 7 way in the back did have a blue wire but traced it about 10 inches and it was just terminated with a cap.
On to doing it the hard way.....
Here is what you will need:
- Brake controller
- 3 wires 8 to 10 gauge will need 5 foot of 2 of the colors and 10 foot of the other
- 1 wire 12 gauge, will need about 15 foot of this wire
- 1 standard DC relay, autozone standard lighting relay (will have pins 87,86,85,30,87A)
- Butt splices reds, blues, and yellows and vampire clips
- Volt meter (Harbor freight special will work)
- 1 Inline fuse holder and 30 amp fuse
- Lots of zip ties
- Will need one more long wire but we will get to that.
- 1 helper (wife, teenager, well trained dog or otherwise...)
print the following picture for reference
Pull the generator tray forward
Locate the brake pedal and the 2 harnesses coming out of it. The higher harness should have 3 wires. The center wire, red I believe, is the service brake signal wire. This works as a negative 12 volts. Use a volt meter and confirm that when your helper presses the brakes that you get negative 12 volts from the wire.
Use the vampire clip and your 12 gauge wire and hook to this wire. Run the wire through the foam sealant on the right side of the RV to bring the wire into the distribution panel area. You are now done up front, close the generator tray.
Using the picture above wire the relay as shown and secure the relay to the wall. I chose to power the relay and the brake controller from the same inline fuse holder which I terminate on the main 12 volt chassis lug. From the fuse holder I used a yellow butt splice and connected two wires to one side of it. Doing this will keep the brake controller powered at all times. This is OK for me as I will be removing mine when not in use. I may install a switch on the inside of the RV if it ever becomes a problem. One of the 2 wires will go to the relay this wire will need to hook to both pins 86 and 30. I used another vampire clip and 3 inches of 12 gauge wire. The other wire will power the brake controller and will eventually be run inside the RV.
Use one of the other wires for your ground and wire it into the panel ground.
Inside the RV go ahead and remove the panel by your left leg when driving. They have button caps that pop off and then phillips head screws.
Back outside to the distribution panel. At this point you have 3 of the 4 wires required for the brake controller. Add a 4th wire to this, 10 gauge, and run all 4 wires up through the foam sealant and into the side panel by the driver seat. Use your helper to pull the wires and all slack through. Make sure to leave a few feet of the 4th un-terminated wire inside the distribution panel area.
Back inside the RV, butt splice all wires to the brake controller wiring harness. Mount your controller and button up the panel.
One last wire to run and boy is it fun.....
You will now need to run a wire from the 7 blade at the back of the RV all the way to the distribution panel area and butt splice it to the previously un-terminated wire.
You have choices here...considering the length you will want a high quality wire....considering the area you will want a well protected wire...
I just happen to have an outdoor extension cord with a bad end on it. The rest of the cord was fine. Obviously you will need one the same length or longer than your RV.
After finally getting the cord run the full length, tucking it out of danger, zip tying it every few feet, you can now butt splice it on the blue wire from the 7 blade. Cut the cap off the end and splice it good. I took 2 of the 3 wires from the extension cord and crimped them together.
On the other end you will either need to run the extension cord into the distribution panel area or run the un-terminated wire out. Either way, splice the same two wires to the un-terminated wire.
Testing....
Have your helper manually active the brake controller while you are at the back with your volt meter. Properly ground the black probe and place the red probe on the blade in the 4 oclock position. While your helper has activated the controller, you should get somewhere around 11 to 12 volts at the back. If lower check your settings on the controller. Tell the helper to release the manual control.
Now have your helper push the brake pedal. You should get some amount of voltage depending on how your brake controller operates. Time delay style should get full voltage as before. Proportionals will get low voltage and they rely on inertia to operate.
Hook up your trailer and take it for a test.
I hope this is helpful to whoever has to do this task in the future. I'm sure I'll be doing other writeups and I tend to do lots mods on stuff.
Even griped-out the trailer-mfgr! 
Linear Mode
