First to market with its TRW branded Electric Park Brake (EPB) system in 2001 – which pioneered with Lancia, Audi and VW – the ZF business has now produced in excess of sixty million EPB motor-on-caliper units.
This article looks at what to do in the event of the brake failing to release, demonstrated in this video.
The cause for this defect is an interrupted power supply to the electric motors (actuators) which then can no longer release the brake. The exact fault can only be identified by experienced professional mechanics using the appropriate diagnostic tools.
To get the vehicle to the garage, however, it may be necessary to open the brake with the emergency release. Some vehicle manufacturers offer integrated systems for this. The exact handling is described in the operating instructions for the vehicle. For vehicles where this is not the case, this piece describes a general option for emergency release.
One important note: Do not attempt to release the brake by connecting an external power source. This can destroy the actuator due to different electric controls for the system variants!
To release the brake, you should therefore proceed as follows:
- Remove the connector
Disengage the connector with a suitable tool and pull the connector from the actuator.
Note: Some EPB systems use actuators with an integrated cable. In this case, the plug connection must be disconnected on the cable harness of the vehicle. This is generally located in the corresponding wheel housing!
5. Mount the actuator
Insert the actuator, ensuring correct seating of the sealing ring.
Note: The motor may have to be rotated slightly during installation so actuator and spindle engage.
Insert the fixing screws
Attention: Ensure to insert and tighten the screws by a few turns by hand. If the thread is damaged, the complete brake caliper has to be replaced!
Tighten the screws with the torque specified by the vehicle manufacturer. Install the connector.
A library of technical tips, ‘How To’ guides, videos and fitting instructions can be found at TRW’s Tech Corner. To register, simply go to: www.trwaftermarket.com/en/Tech-Corner