The convertible top cover is an extremely powerful mechatronic unit. The required forces are provided by the hydraulic cylinder. These cylinder are supplied with hydraulic pressure of up to 200 bar.
The pressure analysis enables detection of faults in the mechanical and hydraulic components of the convertible top cover. Faults that do not yet negatively influence the function are displayed; these do not have to be repaired immediately.
To perform the pressure analysis, connect the car to a battery charger. The vehicle temperature must be between 59°F and 86°F (15°C and 30°C). The pressure curve depends on the vehicle temperature. Hydraulic fluid is very thin and aggressive. Only approved oil may be used. Captured oil must not be reused! When working on the hydraulic components, care should be taken that no hydraulic fluid gets on the cover fabric or upholstery.
If the hydraulic cylinder is moved, it operates like a pump. This means that on the hydraulic system open connections must be protected against spurting hydraulic fluid.
There is the possibility to print the pressure curve with the switching states. The pressure curve is synchronized with the switching states when the hydraulic pressure briefly drops on opening a valve. The printout with switch positions and cover positions makes clear the dependencies on the pressure curve and any faults in the hydraulic and mechanical components. It must always be borne in mind that reduced or increased pressure can be caused by sluggish mechanical movement or a hydraulic obstruction. If the hydraulic line is blocked before the pressure sensor, the pressure is too low. If the hydraulic line is blocked after the pressure sensor, the pressure is too high. Pressure that is too low is also caused by a defect in the cylinder piston seal.
Fault system output |
Action |
(1) No fault can be detected at the moment in the tested component group. |
not required |
(2) ”S239 Convertible top cover case floor does not switch” |
Test module convertible top cover floor (check of switch mechanics) |
(3) ”S188 Position convertible top cover does not switch” |
Test module convertible top cover open (mechanical check sensor) |
(4) ”S142 Locking hook closed does not switch” |
Test module cowl panel locked (mechanical check sensor) |
(5) ”S145 Locking hook open does not switch” |
Test module cowl panel unlocked (mechanical check sensor) |
(6) ”S161 Convertible top cover, right, S161 does not switch” |
Test module convertible top cover lock, right (mechanical check sensor) |
(7) ”S158 Convertible top cover, left, does not switch” |
Test module convertible top cover lock, left (mechanical check sensor) |
(8) ”S164 Hardtop not switched” |
Test module hardtop (mechanical check sensor) |
(9) ”IO1025 Position main pillar incorrect display” |
Test module position main pillar (mechanical check potentiometer) |
(10) ”IO1026 Position rollover bar incorrect display” |
Test module position rollover bar (mechanical check potentiometer) |
(11) ”Convertible top difficult to move” |
Check of hydraulic lines for pinches, move top cover by hand (terminal R off); if hinge suspicious, open hydraulic line (caution: spurts oil when moved) |
(12) ”Convertible cover mechanically or hydraulically blocked” |
Check of hydraulic lines for pinches, move top cover by hand (terminal R off); if hinge suspicious, open hydraulic line (caution: spurts oil when moved) |
(13) ”Establish start conditions” |
Only start cover operation from final position (red LED must not light up) |
(14) ”Convertible cover mechanically or hydraulically difficult to move” |
Check of hydraulic lines for pinches, move top cover by hand (terminal R off); if hinge suspicious, open hydraulic line (caution: spurts oil when moved) |
(14) ”Convertible cover top cylinder, right, defective” |
Replace defective cylinder (caution: spurts oil when moved) |
(15) ”Convertible cover top cylinder, left, defective” |
Replace defective cylinder (caution: spurts oil when moved) |
(16) ”hydraulic pressure too low” |
Check for inner and outer leaks (terminal R on, move convertible cover by hand), frequently defective hydraulic unit |
(17) ”Check hydraulic fluid” |
Fill oil up to mark |
(18) ”Lines 13 and 14 confused” |
Only after repair work, as danger of mixing up lines |
(19) ”Convertible top cover- right or left cylinder piston seal defective” |
Move convertible cover to holding position; move convertible top cover to left and right towards ZU; defective cylinder offers less resistance; replace defective cylinder |
(20) ”Rollover bar - right or left cylinder piston seal defective” |
Move convertible cover to holding position; move convertible top cover to left and right towards ZU; defective cylinder offers less resistance; replace defective cylinder |
(21) ”Check hydraulic unit” |
Check level of hydraulic fluid; if OK replace hydraulic unit |
(22) ”Main pillar - right or left cylinder piston seal defective” |
Move convertible cover to holding position; move convertible top cover to left and right towards ZU; defective cylinder offers less resistance; replace defective cylinder |