May 9, 2017

Reinstalling a SMI Air Force One in a New Vehicle

By: Rob Lowe

Featured Picture

Installation of SMI System BoxWe recently removed an SMI Air Force One from our 8-year old Saturn Vue and re-installed, after refurbishing it, in our new Buick Envision. The refurbishing involved completely checking out all of the components for any damage, since it had been operating correctly in the Vue, and cleaning everything. We wrapped the wiring in marine grade heat shrink and replaced all electrical connectors on re-installation. The system box (yellow arrow) is larger in height than the currently available model and the air cylinder does not have the micro-switch on it to provide the electrical signal that the brake is ‘On’ in the towed vehicle.location of air and vacuum lines

The box (yellow arrow) was mounted in the upper right corner when looking at the engine area, using wire ties to support it over top of a number of ground posts designed to connect ground wires (including this unit’s) to the car’s body. The air connection to the brake pedal air cylinder had an inline air switch (Red Arrow) which reacts to the air pressure change in the air line to the cylinder. The air line had to be routed to clear the hood support strut, which was easily done. The Air Switch operates as follows: When the coach brake is depressed air flows from the coach braking system through to the coach air connection across the hose to the car connector and up to the SMI Operating unit. From there it flows through the air switch and the air cylinder on the brake pedal arm of the towed car which applies the car brakes. The air switch sends an electrical signal through the car connection and cable extension to the coach connector and through the coach wiring to the dash mounted indicator light. In the second photo, the Yellow arrows show the location of the air line from the system box down to the coach connector.  The Red Arrow shows the vacuum connection with the check valve placed in the vehicle’s brake booster vacuum line.
Front of Car
In the photo of the front of the car, you can see the air line connection in the center and the new breakaway switch with the loop hanging down.  The internal connections of the switch were protected against corrosion with Corrosion Block®.

Running the air line through the firewall involved going through two metal panels, with the second panel having the vehicle’s main electrical grommet in it. Since that grommet was recessed, a long installer drill bit was carefully inserted into the edge of the rubber grommet  from the engine compartment side and a suitable hole prepared, then the air line and light wiring were drawn carefully through to the car interior.
ist cylinderThe air cylinder was mounted on the accelerator side of the brake pedal arm, since the steering shaft was directly ahead of the brake pedal and there was no suitable location for the floor mounted cable retainer. By placing the cylinder on the right side of the pedal the retainer could be secured to one of the mounting bolts for the accelerator pedal. The last photo shows this mounting point with the brake pedal wire wrapped through the retainer.
 The system performs well and is hidden from view. The beauty of SMI’s Air Force One is the lack of moving parts (other than the air cylinder) completely safe attachment to the coach air system and the power brake on the towed vehicle works as if it was being driven. Moving the system from one towed vehicle to another is a straight forward procedure, delivering excellent safety with minimal additional cost.

For More Information, check out our Braking pages on the website.


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