Bomag BW 156 D-3, Service Manual

Page: 146 / 190

Service Training
BW 156/177 D-3/PD-3 - G 5 -
BW 178/179 D-3/PD-3
Ignition switch (S00) in position "0" (ignition off)
The ignition switch (S00:04) is permanently supplied with current from the battery (G01) (Fig. 1) via main
fuse (F00) (potential 30) and fuse (F13:05).
In this position the connection to the coil of relay (K11:28) is interrupted and the relay drops off. The
solenoid valves (Y58:32) for fuel shut-off or (Y13:37) engine solenoid (depending on engine version) are
no longer supplied with current and the diesel engine will stop.
Ignition switch (S00) in position "1" (ignition on) with the engine at rest
In this position the coil of relay (K11:26) is supplied with current.
• Relay (K11) switches potential 30 to potential K11 (15/54). Fault monitoring unit (A15) (Fig. 3)
supplies the coil of relay (K22:40) with current, the relay switches. Current flows
• from potential K11,
• fuse (F14:37),
• the closed EMERGENCY STOP switch (S01:37),
• the closed contacts of relay (K22:37)
• to solenoid valve (Y58:32) for fuel shut-off or (Y13:37) engine solenoid.
The engine is ready for starting.
Ignition switch in position "3" (starting)
Note:
Position "2" is not used.
In this switching condition current flows from terminal 50a on ignition switch (S00:06) to the contact of
relay (K05:07).
When the travel lever is in "0" - and brake position the contact of proximity switch (B13:15) opens, the
coil of relay (K48:15) is no longer excited and the contact switches over.
Current flows
• from potential K11,
• via relay (K48:17),
• to the coil of relay (K05:09).
The contact closes and current can now flow to the starter (M01:05) terminal 50. The magnetic switch
of the starter is excited and the starter cranks the diesel engine.