How many fans/blowers does the aircon system on a W202 have. When I press the EC button (on/off) I normally can hear a "second" blower kicking in when aircon is engaged.

Sometime this 2nd bloer is on and sometimes it is off when the aircon is engaged. Its normally when this 2nd is not blowing (while aircon should be on) that I dont get the desired cooling.

How does this 2nd blower works?