Maintenance manual for sunray hfc4da1-2c china-IV diesel engines
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11.Dual brake switch
1) Overview
The dual brake switch is located on the upper portion of the brake pedal and internally incorporates two independent
switches.
2) Working Principle
The brake switch monitors the action of the brake pedal and transmits the signal measured to the engine ECU. The
brake switch is equipped with two switching mechanisms, which are the main and secondary units of the brake switch.
When the signals from both units are inputted, the engine ECU will judge as normal braking signal. These switching
signals are related to the accelerator pedal and are used to control the fuel amount during the braking. This means that
the operation of accelerator pedal will not lead to malfunction when the brake pedal is stepped down, but the operation
of accelerator pedal will reduce the fuel amount when the brake pedal is stepped down.
3) Measurement analysis
12. A/C switch
1) Overview
The A/C switch is located on the A/C control panel and is mainly functioned to transmit actuation directive of A/C
compressor to the engine control unit.
2). Working Principle
A/C request is the input signal that the driver requests the working of A/C and controls the working of A/C relay as
well as the speed promotion of the engine.
3) Measurement analysis
4) Malfunction Mode:
z Short-circuit or open-circuit of signal circuit;
z Unstable signal;
z The signal is out of range.
Low pressure
High pressure
A/C switch
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