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ELECTRIC CIRCUIT
CASE TRAINING CENTER
AUGUST 2000
Automatic engine pre-heat
1) Circuit configuration
CS00F514
1. Instrument panel
2. Main electronic control box
3. Starter motor switch
4. Engine electronic control box
5. Pre-heat glow-plug relay
6. Engine
7. Pre-heater plug
8. Engine coolant temperature sender
9. Electronic acceleration
2) Operation
1. When the ignition switch is turned on (IN1 = ON), the main electronic control box (2) calculates the pre-heating
time (Tp) by means of the engine coolant temperature (see figure).
2. The engine electronic control box (4) activates the pre-heat relay (5) for the pre-heating time (Tp) previously
calculated and transmits a signal to the main electronic control box (2).
3. At the end of pre-heating time (Tp), the pre-heat relay (5) stays on for 2 seconds more.
4. When the ignition switch is turned (3) to "START" (ST, IN2 = ON), the engine electronic control box (4) reactivates
the pre-heat relay (5) but does not transmit a signal to the main electronic control box (2).
5. The engine electronic control box (4) calculates the time after pre-heat (Ta) by means of the engine coolant
temperature (see figure).
6. When the ignition key (3) is turned back from "START" to "ON" (IN1 = ON; IN2 = OFF), the engine electronic control
box (4) activates the pre-heat relay (5) for the time after pre-heat (Ta).
7. During the time after pre-heat (Ta), the message "ENG. PRE HEAT" appears on the control screen (LCD).
8. The control system mentioned above immediately starts, with the ignition on, the message "ENG. PRE HEAT"
appears on the control screen (LCD) only if the pre-heating time exceeds 3 seconds (engine coolant solution
temperature below -5°C).
NOTE: When the ignition is switched on, the "CASE" logo appears on the control screen (LCD) for 3 seconds.
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