Braking System for Tow Vehicle

Golden_HVAC wrote:
I have a cruise control motor on my toad, and the cable from it pulls the brake pedal to the floor, all for about $35.

I took a cruise control motor off a junkyard Nissan, it is about 3" diameter, and fits under my dash easy. I had one from a Taurus on my Honda, and it was about 4" diameter, and pulled 'to hard' so the smaller diameter is actually OK.

The cable goes to a bracket on my floor, then to a clamp on the brake pedal arm. It is attached about 2" above the brake pedal rubber pad. Lower and it will give more braking effort, higher and it has less leverage, so will offer less effort. Mine is "About right" and when driving down a long grade on a 2 lane highway, I 'rode the brakes' on my motorhome, applying them just enough to turn on the brake lights, and activate the vacuum solenoid that applies engine vacuum to the power brakes on my car. At the bottom of that hill (about 3 miles at 6% grade) there is a rest area, and I checked the brake rotor temps. They where acceptable.

For the car, I have a 5' section of 3/8" air hose cut off a 50' long piece, and with the 3/8" air line connection at the end, with the tool end of a quick connect air fitting. It goes to a tee, then to the power brakes where there is a check valve, then another tee, and a check valve between this point and the engine, so that the car air intake does not leak air into the line when in the towing mode, but will allow free airflow into the car intake system (for power brakes while not towing). So air must leave the power brake reservoir towards the RV when towed, and towards the car engine while driving it, but not flow backwards in either case, so that you will not lose power brakes should the engine shut down while driving the Toy.

The other side of that tee is to the vacuum solenoid, and then to the cruise control motor. It must be a 3 way solenoid (got it from a junkyard car too) and it will let in air to the CC motor to release it when the brake lights are off. Power from the brake pedal (not the turn signal) goes to the solenoid. Like from the third brake light (if you have one) or from the wire leaving the brake pedal switch and going up towards the turn signal switch. When brake lights are on, vacuum is applied to the CC motor, when off, then air can enter the CC motor to release it. Check it by finding the common fitting. It not marked, you can blow through 2 ports, then when applied 12 volts through two points. The Normally open is one, that will be closed when you have 12 volts, and is the air into the CC motor. The NC will not pass air when off, but passes vacuum into the CC motor while energized. Common port goes toward the CC motor, and is open to one while off and the other port when on.

Sorry DP owners, it only works on gas engine RV's or those with a vacuum source. On my gas engine, I was able to find a 3/8" vacuum fitting. I took off the cap, and installed the other side of the 50' 3//8" hose. I tie wrapped it down well under the chassis to the frame, and kept it away from hot exhaust lines. The quick connect on the RV end does not pass vacuum when the engine is on in the RV (unless connected to the toad vacuum line), so you can still drive it while going without the toad.

Good luck, and write back if you need me to talk about this. You might need to send me a PM, and I will share the details here.

Fred.

PS: While this has worked on my RV, I am not to sure it will work for anyone else. . ..

Thanks to Fred, I also built this vacuum operated system. Only difference is that my CC motor (Jeep Grand Cherokee) has the necessary valves built in, so all I needed was to wire them to my brake light via the tow connector, and add a tee and check valve to the vacuum system. Works absolutely perfect! My sincere thanks to Fred for the inspiration.