Mine make rattling noise, the arm moves and the inertia sensor moves. They are supposed to.
Like said above, plug it in, sit it on the passenger side floor and go for a drive that includes stopping, and slowing. Watch to see if the arm that attaches to the brake peddle moves out then retracts. If it does it is working.
Keep in mind that a Brake Buddy will drain your car battery in four or five hours of towing behind your rig. You will need to run a charge wire from your MH to the toad to keep the battery from discharging.
Fun but dirty job running a wire from front to back but you get to know your MH undercarriage intimately.
Discharge your toad battery just a few times and you will be buying a new one (speaking from experience)
Safe Travels
