U
Charger
alternator
9
V
W
Stator
Brush
Brush
Exciter
coil (rotor)
Excitation
controller
B+
D+
W
1N4007
Rex
25
24
12
18
17
Running
feedback
- +
Battery
Run coil
RPM
input
Rex: Excitation resistor
12 V systems: 47 Ω 4 W
24 V systems: 100 Ω 6 W
At standstill, the b is connected to terminal 9 (common), and a current flows to terminal 12 and via the
D+ input on the alternator to ground (battery -). When the starter is engaged (cranking), the battery will supply
the D+ through the REX resistor, helping the alternator to excite. When the alternator starts to produce volt-
age (excitation OK), the speed of the alternator will be above running speed, and the voltage on term. 12 will
rise to a value higher than the battery voltage and then interrupt the current flow through REX and activate
the running feedback input. Engine is running.
If a stop coil is used, the REX resistor can be connected to the starter relay (crank).
GCU 100 installation instructions
4189340799 UK
Wiring
DEIF A/S
Page 15 of 31
