One other comment. I don't know it MB does this but some cars use sensors that will not be activated in water. By putting water in the reservoir the light won't go out. It will as soon as the water mixes and the necessary mixture is present at the sensor.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician
[This message has been edited by stevebfl (edited 09-04-2000).]