The automatic convertible top is a hydraulic system that is controlled by the convertible-top module. The convertible-top compartment-lid lock and the convertible-top lock are opened electrically.
The convertible-top module registers the positions of the convertible top and controls the hydraulic system as well as the electrical drives for the convertible top and the locking mechanism. In addition, the occurring faults are stored and output.
The positions of the main pillar and of the tensioning bow are registered by potentiometers. These potentiometers are designed as electronic components i.e. not resistors. The adjustment range is proportional to the voltage drop across the potentiometer. The position of the tensioning bow is dependent on the position of the main pillar.
The hydraulic system of the convertible top consists of various assemblies: The hydraulic unit, valves and cylinders. V5 (pressure cutout valve) must be activated for the purpose of generally enabling the hydraulic system. After terminal R has been switched off or after 15 minutes without operation, V5 depressurises the entire system in stages. As of model year 09/2001, the V5 has been phased out and not replaced. It is not possible for the convertible top to collapse, as the hydraulic pressure between the valves and cylinders is blocked.
Note: the convertible top moving in jolts is an indication that the battery charge is very low. For testing in the workshop, a battery charger must be connected..
The hydraulic unit makes available the oil pressure for moving the convertible top. Two pressure relief valves ensure the oil pressure does not reach critical values. Only the function that has already been triggered can be completed if the pump temperature increases to above 95°C. The convertible top must be moved by hand at a temperature above 105°C. The hydraulic fluid can be checked when the convertible top is lowered.
The hydraulic valves are electromechanical components for controlling convertible top operation. The convertible-top module cannot detect mechanical defects. A slight mechanical knocking sound during operation is a sure indication that the hydraulic system has been enabled.
The hydraulic cylinders are used as the drives for convertible top movement. The advantage offered by the hydraulic system is the high degree of power transmission.
Important
It is important to ensure that the complete system is connected correctly and work is always carried out with the system depressurised. The system in the holding position at zero pressure or when terminal R is disconnected.
The electrical drives serve the purpose of locking the convertible top and the convertible-top compartment lid. These drives have a high power consumption.Caution - risk of injury by high mechanical forces.
The Hall sensors are power switches where a value of 4 mA equals ”switched” and 15 mA ”not switched”. Ferromagnetic material must be positioned at least 1 mm in front of the sensor so that a switch can detect an object.
There are two Hall sensor circuits in the vehicle, i.e. the convertible top sensors and the body sensors. If the positive supply has a short to ground, all sensors of the affected circuit will be switched off.
The convertible top position is defined by the angle value of the main column and tensioning bow potentiometer. The position of the tensioning bow is dependent on the position of the main pillar.
The ground-switching microswitch for "convertible top compartment floor down" signals the position of the convertible top compartment. The convertible top cannot be opened when the compartment floor is not down. This status is indicated by the green LED in the switching centre of the centre console illuminating when the switch is pressed.
If there is no fault memory entry and the convertible top cannot be moved automatically, this may be caused by the following.
Symptom |
Help |
Convertible-top movement is not fully completed, no further movement possible. |
Disconnect terminal R, operate lock by hand until LED stops flashing. Repeat procedure if necessary. |
Convertible top moved to intermediate position and movement interrupted. Convertible top no longer moves after some time. |
Convertible top in implausible position. Stow convertible top by hand in convertible-top compartment. |
Convertible top movement is not complete; hydraulic unit working; with support by hand, no further movement is possible. Pump supplying full pressure. |
Implausible switch position. Check all switch positions. After repair work, cables may have been mixed up. |
Convertible top movement is not complete; hydraulic unit working; with support by hand, further movement is possible. Pump supplying full pressure. |
Internal leak of a hydraulic cylinder. Check all cylinders. |