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On most cars, there's a direct mechanical linkage between the driver and the parking brake. However, in a short-but-growing list of vehicles, an electronic control unit operates the parking brake. The driver can still apply or release the brake with a button, but these systems can also operate automatically. Some apply the brake in park; some apply the brake when the vehicle comes to a full stop, when the trunk lid is open or under several other scenarios. To unlock the brakes for service and to prevent nasty surprises while working on the vehicle, make sure your technician customers know how the control unit "thinks" and how to disable it.
The other type has a motor on each rear caliper that mechanically operates the caliper piston. It can be found on Mercedes-Benz vehicles, Audi A6 and A8 models and the Volkswagen Passat. In each system, the control unit operates the motor in both directions as needed, just like a window lift motor. In fact, the motor itself may be exactly the same as a window lift motor but with a transmission to multiply its torque. By themselves, EPB systems are not strong enough to stop the car quickly, but they will hold it in place.
Even if a technician decides not to tackle these jobs, he or she still needs to know how to manipulate the system for normal maintenance procedures, such as replacing the car's battery or retrieving it from the roll-back. |
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