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Electronic parking brakes, their problems and their solutions
The purpose of this section is to avoid disappointing you by being us unable to solve your problems. This information should tell you whether we can help
What are we talking about?
The box and it’s fittings inside Renault; Scenic, Grand Scenic Laguna and Espace which controls and operates the automatic parking brake
All the units described here are made by Küster for Renault and have a wide range of part numbers of the form 8200****** where the last six digits can be almost anything. They are a sealed black plastic box of approximately 30cmx 15cm x 6cm with various mechanical cables and an electrical wire on one small end face. All units have an emergency release cable entry gland on the opposite face.
What is inside the parking brake unit?
All units contain the same powerful motor/gearbox combination. This drives a (turn-
What goes wrong?
The motors suffer from wear to the brushes Our experience is that complete motor failure can occur from 70,000 miles onwards and accounts for some 80% or so of failures we see. Another significant cause is the PCB mounted relay which changes the sense of the drive current for the motor, and hence its direction. The relay accounts for many failures and, in the case of the smaller later type, can often be seen to have a slight doming, or even a bubble of melted plastic on top indicating it is either at or near the end of its life. We suspect that the high current surges associated with motor failures over-
The traditional repair approaches
When they go wrong, the received wisdom in the car repair industry has been that these units are irreparable and replacement with a new unit supplied by a Renault distributor is the only reliable long term solution. Other repairers have fitted second hand units from breakers.
For a new unit, you need to programme the replacement with, information about which engine and gearbox etc. are in that particular car. In the case of manual cars, it must “learn”information about the specific clutch pedal of that individual car.
For the second hand unit, you don’t know what it’s been through and may be only a short time away from failure. Second hand units will often work, but for optimum performance on hill starts etc, they require re-
What Blue Chip Autotronics do to repair or refurbish these units
We read the fault codes with our diagnostic machine. If there is reference to a motor fault code, either existing or historic, we will treat it as a straightforward motor failure, If historic, we cannot be certain that the motor is the root cause because the relay is capable of causing the same fault as the motor, and both the motor and relay can become intermittent. We will change both motor and relay in this case.
Sometimes there are other codes as well as motor codes. This is often because repair attempts appear similar to a random selection of other faults
We have found that
The Scenic unit has a single brake cable of approximately 1m which terminates in a triangular steel “shoe”which slides within a force divider assembly situated centrally on the rear axle. There are a pair of opposed Bouden cables from the force divider to the calliper assemblies.The unit itself is mounted behind the rear right hand wheel arch and within a plastic cage. Rubber bushes provide some vibration isolation. This is shown here
Grand Scenic Laguna and Espace
The Grand Scenic, Laguna and Espace units have an opposed pair of cables emerging from the small faces. The cable types are similar, but not identical. The Grand Scenic unit is mounted in a plastic cage, again via shock absorbing rubber bushes. The Laguna unit is similarly mounted but in a steel assembly. All are situated centrally between the rear wheels. The cable routing and fitting is straightforward.
These cables have several different termination arrangements and lengths according to year and model variant. All are straightforward to remove and refit, some terminating underneath the car, some within the boot space. The owner’s manual should be consulted if problems arise. The gland which they pass through into the box is frequently broken when we see them. This rarely causes an operational problem, but may permit water to enter and track through the gland, which can be disastrous. However, we have a “fix”which we retrofit routinely when refurbishing units.
How do I know what is wrong with my parking brake?
Firstly, you need to establish that the parking brake unit, as opposed to anything else, is at fault. This is next to impossible without diagnostic equipment. We don’t wish either to endorse or condemn a range of diagnostic tools, so will only comment that we know the performance of DEC Superscan III and Renault CLIP to be satisfactory and that some relevant fault codes will not be read by some other tools. Please search Internet forums for guidance on tools. It may save a good deal of frustration if you don’t jump immediately to the conclusion that the parking brake unit must have failed. There can be fault codes logged in the unit that prevent its proper operation but are caused by mechanical failure external to the unit. We are happy to help and advise with these fault codes.