SYSTEM / Electrical System WORKING LIGHT CIRCUIT Working Light and Cab Light Circuit 1. When the working light switch moves to position 1, monitor unit terminal #B20 receives the signal. 2. Terminal #A1 is connected to the ground inside the monitor unit. 3. Therefore, light relay 1 is excited, current from fuse #29 flows to the working light and cab light, and turns on the working light and cab light. Boom Light Circuit 1. When the working light switch moves to position 2, monitor unit terminal #A6 receives the signal. 2. Terminal #A5 is connected to the ground inside the monitor unit. 3.
Therefore, light relay 2 is excited, current from fuse #1 flows to the boom light, and turns on the boom light. T2-5-22