Automatic Convertible Top

Automatic Convertible Top

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.

Conditions for convertible top movement
- Rear lid closed
- Non of the side windows must be closed by the GM
- Speed < 5 km/h
- No hardtop fitted
- Terminal R or convenience function
- Convertible top compartment floor at bottom

Opening procedure
1. Press "Open" switch
2. Windows are lowered
3. Convertible top is unlocked at scuttle
4. Tensioning bow is raised
5. Convertible top compartment lid is unlocked
6. Convertible top compartment lid is opened
7. Tensioning bow is lowered
8. Convertible top is lowered into convertible top compartment
9. Convertible top compartment lid is closed
10. Convertible top compartment lid is locked
11. 2 seconds waiting time, the side windows are then closed

Closing procedure
1. Press "Close" switch
2. Windows are lowered
3. Convertible top compartment lid is unlocked
4. Convertible top compartment lid is opened
5. Convertible top is lifted out of convertible top compartment
6. Tensioning bow is raised
7. Convertible top compartment lid is closed
8. Convertible top compartment lid is locked
9. Tensioning bow is lowered
10. Locking mechanism pulls convertible top onto scuttle and locks
11. 2 seconds waiting time, the side windows are then closed

Convertible-top module (CVM)
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.

Convertible top positions
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.

Convertible top hydraulics
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 depressurizes 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 degree C. The convertible top must be moved by hand at a temperature above 105 degree 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.

Electrical drives
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.

Hall sensors
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.

Convertible top position
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.

Convertible top compartment floor
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 center of the center console illuminating when the switch is pressed.

No fault-memory entry
If there is no fault memory entry and the convertible top cannot be moved automatically, this may be caused by the following.