The primary function of the trailer breakaway switch is to apply the trailer brakes in an emergency situation and the secondary function is to operate as a parking brake.

Prepare for the Automotive Service Technician Period 1 exam. Study with flashcards and multiple choice questions, each question has hints and explanations. Get ready for your exam!

The main idea is that a trailer breakaway switch is a safety device that automatically energizes the trailer’s electric brakes if the trailer becomes detached from the tow vehicle. It uses a small battery on the trailer to power the brake circuit when the breakaway pin is pulled, quickly applying the brakes to prevent a runaway trailer. The secondary function is to hold the trailer brakes on as a parking brake when the trailer is stationary or unhooked, using the power from the breakaway system. In practice, this means the device is designed for emergency stopping and can also provide a brake hold when needed, which is why this statement is true.