That is not a low coolant light. That is a general cooling system alarm light.

IT comes on:

If coolant is low.
If coolant level sensor is bad.
If engine fan motor is bad.
If fan control module is bad.

MOST of the time, when it comes on, the A/C is disabled to reduce load on the engine and cooling system as a precaution to prevent overheating the engine. If your fan motor/controller are acting up, the light comes on and the A/C may cut out.
The most common cause is a bad coolant level sensor in the tank but we are seeing more and more Fan Control Modules fail as our cars age. IF you want a new one, the one from the Mercedes SLK320 (2003) fits. Ordering a Crossfire part usually results in "No longer available".