The lever is just a piece of metal attached to the valve. it can't really be defective unless it's broken.

The valve, on the other hand, can be easily checked from under the car: if you push it up, the struts should fill with more fluid and the rear of the car should raise up. Alternately, if you push the lever down, the fluid in the struts should release and the back of the car should gradually move back down.

If the valve is faulty one or the other or both of these conditions would result in no chance to the ride height of the car.

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'94 W124.036 249/040 leder; 8.25x17 EvoIIs
'93 W124.036 199/040 leder; 8.25x17 EvoIIs, up in flames...LITERALLY!
'93 W124.036 481/040 leder; euro delivery; 8.25x17 EvoIIs
'88 R107.048 441/409 leder; Euro lights
'87 W201.034 199/040 leder; Euro lights; EvoII brakes; 8x16 EvoIs - soon: 500E rear brakes
'70 R113.044 050/526; factory alloys; Euro lights