Nilfisk-Advance SC900-28D Service Manual

Contents

52Service Manual – SC900 34 - Scrub System, DiscCircuit OverviewThe brush circuit has several prerequisitesto operate All of the following must to betrue for the brushes to run:• Key switch on• Battery Voltage not low• Machine in motion (even if zero speed)• Brush deck loweredStarting at the motors and working backtoward the batteries; the brush motors areconnected directly to battery negative Onthe positive side, each motor has its owncircuit breaker, which is downstream fromthe K2 relay contactThe control coil of the K2 relay is in serieswith the brush (deck lift) switch and theK1 relay This circuit receives power fromthe Drive Controller’s Brake output, whichis active only when the drive controller iscommanding motion The positive side isalways energized when the controller isenabled, and the negative side is switchedto ground voltage when the machine is inmotionThis circuit of the K2 coil, Brush Switch,and K1 relay, along with the DriveController’s Brake output, provides thefundamental control of the brush motorThis circuit is active only when all 4 of the prerequisite conditions mentioned above have been metThe control coil for the K1 relay is in series with the hour meter This aspect of the circuit provides thelow-voltage cutout feature to disable the scrub system when the batteries are running low The hour metercontains a Field Effect Transistor (FET), which is active (conducting) when the battery voltage is sufficientfor operation The FET acts like a switch which connects the negative side of the relay coil to groundWhen the key switch is off, it disables the drive controller and also the K1 relay This effectively disables allmachine functionsBLKBLKPNK/WHTVIOPNK/BLUVIO/WHTPNK/BLUVIOPNKPNKS1SW, SPST KEYS4SW, BRUSHRELAY, LVC123456CURTIS 1228KSI5BRAKE-6BRAKE+14D2K1 RELAY, LVCBATTERY GAUGE WITH HOURMETERFET DRAIN3 B- 4D136 VDC+ -K2COIL, BRUSHK1RED/GRNWHT/REDWHT/RED RED/BRNMM2MOTOR, BRUSH LEFT- +MM3MOTOR, BRUSH RIGHT-+CB325AK2BRUSH CONTACTCB225A