Yellow arrowed switch is for the windscreen wipers on my 120Y. The fan (blower) is turned on by one of the two slides on the front of the heater. The red arrowed vent is flow through ventilation, push it in to let air flow out, air speed is reliant on road speed, the faster you're going the faster the air. A problem I found with my 120y is that there is usually a broken screw that cuts all power to the fan. That screw is the screw joining the resistors that cause the speed to drop. It also happens with the B310 Sunny. there is a little plastic fitting in the heater body that the wires go to, this can be removed & there are two coiled wires on the inside. I usually grab a small screw & nut & replace the broken one, which is usually plastic.