Section 2 – SR-2 Hardware Description
Intake Air Heater
The intake air heater is located at the inlet to the
intake manifold of the diesel engine. The intake air
heater is energized and LED 3 is lit when the
microprocessor energizes the K2 Preheat Relay.
The K2 Preheat Relay normally open contacts
supply power via the H wire to the intake air heater
to preheat the engine before starting. The circuit is
protected by the 60 amp fuse F5.
Starter Motor (SM)
The starter motor is located on the door side of the
engine. The starter motor is energized and LED 25
is lit when the microprocessor energizes the K7
Starter Relay. The K7 Starter Relay normally open
contacts supply power via the 8S wire to the starter
solenoid to crank the engine. The circuit is
protected by the 40 amp fuse F3.
Fuel Solenoid (FSH, FSP)
The fuel solenoid is located at the rear of the injector
pump and is used to start and stop the flow of fuel to
the diesel engine during diesel mode operation. The
fuel solenoid features two coils, a pull-in coil and a
hold coil. The pull-in coil transfers the fuel solenoid
to the open position. The hold coil maintains the fuel
solenoid in the open position.
The hold coil is energized in Diesel Mode when the
microprocessor energizes the K1 Run Relay. LED 6
is lit when the Run Relay is energized and the
contacts have transferred. The K1 Run Relay
normally open contacts supply power from the 8 wire
thru the normally closed Diesel/Electric relay to the
8D wire to energize the fuel solenoid hold coil. The
circuit is protected by the 15 amp fuse F2.
The pull-in coil is momentarily energized and LED
24 is momentarily lit in Diesel Mode when the
microprocessor energizes the K6 Fuel Solenoid Pull-
in Relay for 2 seconds. The K6 Fuel Solenoid Pull-
in Relay normally open contacts supply power via
the 8DP wire to the fuel solenoid pull-in coil to
positively open the fuel solenoid. The circuit is
protected by the 40 amp fuse F23.
High Speed Solenoid (HS)
The high speed (throttle) solenoid is located behind
the fuel injection pump. The high speed solenoid is
energized and LED 5 is lit when the microprocessor
energizes the K3 High Speed Relay. The K3 High
Speed Relay contacts supply power to the 7D wire
to the high speed solenoid to enable high speed
operation.
Alternator Frequency
Alternator frequency is monitored by the micro-
processor via the “W” wire. The alternator frequency
is used for diagnostic and backup control purposes
on model 30 units. It is used as the speed sensor
on model 50 units when operating on electric
standby.
2-27
31 January 2005
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