DC POWER DISTRIBUTION (FIGURE FO-1, SHEETS 2 AND 3) - Continued
When the ECS is set to START, starter motor relay (SMR) A1 K4 is energized. +24 Vdc is applied through the
ESPB (if it is not pressed) and D2 to relay SMMS which enables the starter and cranks the engine. D2 prevents
voltage from the DEAD CRANK SWITCH from applying power to Relay Field Flash (KFF) relay.
Field Flash Relay
Relay A1 K4 also applies +24 Vdc to the coil of KFF relay. The contacts of KFF apply the +24 Vdc, which is
across the coil of KFF, to the generator field coil input (see FO-1, sheet 4) through a 15 Ohm, 25W resistor and
diode CRFF (Diode Field Flash). Note that for the acronyms KFF and CRFF, the common reference designators
for a relay (K) and a diode (CR) were used. This excitation voltage starts the generator generating voltage. After
the process is started, it is self sustaining.
Electronic Governor Relay (EGR) Comm Data Links, MPU, CTR, and GFR
The Electronic Governor Relay (EGR) output of the GSC is connected to the engine controller. P7-21 and 22 are
the Communications Data Link between the GSC and the Communication Module (CM). P7-1 and 2 are the
inputs from the engine Magnetic Pickup Unit (MPU). This pickup measures speed of rotation of the engine by
detecting the starter ring gear teeth. This input is a frequency proportional to engine speed. P7-19 and 20 are
the Communications Data Link between the GSC and the electronic control module on the engine. (This is also
known as the CAT Data Link.) A1 F1 (Labeled F1 GSC on schematic), and the GSC relay contacts labeled CTR
are not used. P7-23 is a low fuel level input from the low fuel level sensor connected to Alarm Module A2 (FO-1,
sheet 3). This input is connected to ground when the fuel tank is almost empty. The 10A fuse between RM-34
and RM-7 is A1 F5. The Generator Fault Relay (GFR) K2 in the GSC closes when the GSC detects a generator
fault. This energizes the GFR external to the GSC. The contacts for the GFR are used to de-energize K1 and
disconnect the load from Generator G1.
Engine Control Switch (ECS)
The ECS consists of two sections. One section consists of pins 1, 2, 3, 4, and 5; the other section consists of
pins 6, 7, 8, 9 and 10 of the switch. There is a legend on the schematic that describes which contacts are closed
in which positions of the switch. Pins 6 thru 10 apply power to the GSC, Overload and Short Circuit (OL/SC)
module, and DVR whenever the switch is not in OFF. This allows the OFF position of this switch to reset any
alarms that have occurred. Shorting pins RM 1 and RM 2 on the GSC does this. Note the internal relay
connections in the GSC between pins RM 1 and RM 2. This is to ensure that power can not be removed from
the GSC when the Fuel Control Relay (FCR) A1 K7 is energized (signifying the engine is running) or the Crank
Termination Relay (CTR) A1 K3 is active (signifying that the engine is running and the starter can be released).
Pins 1 thru 5 ground a different input line to the GSC for each position of the switch, telling the GSC what to do.
Power to ECM, DVR, OL/SC, Fuel Gauge, Panel Lights, Winterization Kit
Fuse F10 shown between RM 1 and RM 10 is A1 F10 on the back of the GSC. This connects +24 Vdc to pin RM
39 whenever the ENGINE CONTROL switch is in any position other than OFF. Slave Relay (SRY) is connected
to RM 39 and is powered up any time the ECS is not in OFF. The contacts of SRY apply +24 Vdc from the
battery to ECM A8. Power to DVR A3 module also comes from RM 39. Power to the OL/SC module comes from
RM 1 through a set of normally closed contacts on relay AR. AR is energized when the LAMP TEST button is
pressed on Alarm Module A2. The fuel gauge (FLG) is connected to RM 39 for power. The signal comes from
the fuel sending unit (FLSU) in the fuel tank. The panel lights get their power from RM 2, which has power
whenever the DEAD CRANK SWITCH is set to NORMAL. Closing the PANEL LIGHT switch (PLS) applies power
to the lights.