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| Illustration 1 | g00297407 |
Main Display Module (1) Alert Indicators. (2) Display area. | |
The main display module continuously monitors all machine systems. The main display module makes decisions that are based upon the input from the machine systems or other electronic control modules. The main display module sends information to other electronic controls on the machine. The input and output of this information takes place over the CAT data link. The outputs on the main display module notify the operator and the service person of the status of the machine systems. The following outputs are on the Caterpillar Monitoring System: the quad gauge, the main display module and the action alarm. A connector with 40 contacts is located on the rear of the module. This connector connects the necessary harness wiring to the inputs and outputs.
Inputs/Outputs
CAT Data Link
The CAT data link (connector contacts 5 and 14) is used to communicate with other electronic control modules on the machine. The CAT data link is bidirectional. This allows the modules to input the information. Also, the modules can output the information. This permits sharing of information such as engine oil pressure, and diagnostics.
Display Data Link
The display data link (connector contacts 15, 25 and 35) provides the electrical signals in order to operate the display module. These display modules provide information about the machine systems to the operator. Each module and each display indicator is identified by an identifier or an address. Data is continuously output from the main display module to the other display modules. The module that is addressed returns the data to the main display module. This confirms the receipt of the data.
Inputs
The inputs tell the main display module the way to operate, and the status of the engine systems. Three types of inputs exist: switch input, sensor input and sender input. Switches and harness wiring provide a ground to the switch or an open signal to the switch inputs. Sensors provide a changing signal to the sensor inputs of the main display module. Senders provide a changing resistance to the sender inputs of the main display module.
These inputs are programmed at the time of installation in order to define the components that are monitored. In order to determine the inputs on the main display module that are programmed, see the Electrical System Schematic in the Service Manual.
Switch Inputs - Uncommitted
The following connector contacts are the uncommitted switch inputs: 7, 9, 11, 17, 19, 20, 21, 26, 29, 32, 36, 37, 39 and 40 During normal operation, these switch inputs are open.
Switch Inputs - Programming
The programmed switch inputs are the following connector contacts: 3, 6, 12, 16, 22 and 31 The operation of the main display module is determined by the programmed switch inputs. The main display module operates in a manner that corresponds to the open state or the grounded state of the programmed switch inputs. These inputs receive information from a permanent connection. The inputs for the programming switch consist of the information from the harness code.
The inputs from the harness code switch tell the main display module the engine model. Information of the model is necessary because of the differences in the engines. Information from the machine is necessary for the main display module to make decisions.
Switch Inputs - Service
The inputs from the service switches (connector contacts 23, 33 and 18) control the setup, the mode of operation, and certain diagnostic functions. Grounding the service input (connector contact 23) and the clear input (connector contact 33) at the same time will initiate a change in the monitoring system mode of operation. Removing ground from these two inputs locks the main display module in the selected mode. Other diagnostic functions are also performed when the service inputs are grounded and/or opened at the proper time. The Left Hand/Right Hand switch (connector contact 18) allows one gauge to display values from two sensors. The switch changes the gauge display from the sensor on the left side of the engine to the sensor on the right side. See System Operation, "Modes Of Operation" for more information on these switches.
Sensor Inputs - PWM
Each PWM sensor input (connector contacts 8, 10, 27, 38) may be programmed in order to operate as either a sensor input or a switch input.
A PWM signal is present when the sensor input is programmed to operate as a PWM sensor input. A PWM signal represents the condition of an engine system. As the condition of the engine changes, the duty cycle of the signal changes. The duty cycle is the percentage of time that the signal is ON compared to the time the signal is OFF. The frequency of the signal is constant. The following examples are conditions that are monitored: temperature, pressure and level. The main display module measures the duty cycle of the output for the PWM sensor. The information is then sent to the quad gauge in order to be shown on one of the gauges.
Note: See "Switch Input - Uncommitted" for input operation when the PWM sensor input is programmed to operate as a switch input. Use the Electrical System Schematic of the engine that is being serviced in order to determine the inputs that are programmed.
Note: The input from the PWM sensor may be programmed to operate a gauge or an alarm indicator. The sensor can also be programmed to operate both a gauge and an alarm indicator.
Sensor Input - 70-800 Ohm
Connector contact 28 is used as a sensor input.
The 70-800 ohm sensor input measures a resistance value in order to read the condition of the system. The temperature sensor (or a component with a similar output signal) provides this information. The output resistance of the temperature sender corresponds to the temperature of the fluid that is being measured. The main display module measures the resistance value. The information is then sent to the quad gauge in order to be shown on one of the gauges.
Note: The 70-800 ohm sensor input may be programmed to operate a gauge or an alarm indicator. The sensor can also be programmed to operate both a gauge and an alarm indicator.
Input - Voltage
The input for battery voltage (connector contact 1) provides the main display module with power. The voltage input is also used by the main display module to monitor the engine electrical system. This information from the voltage helps determine the condition of the electrical system.
An alert indicator is used in order to indicate when the system voltage is less than 23.0 volts for at least 2 seconds or the system voltage is greater than 32.0 volts for at least 2 seconds.
Outputs
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| Illustration 2 | g00297407 |
Main Display Module (1) Alert Indicators. (2) Display area. | |
The outputs of the Caterpillar Monitoring System notify the operator of the status of the engine systems. The main display module provides electrical power for the other display modules and the sensors.
The following outputs are on the Caterpillar Monitoring System: the display (2) for the main display module, the display data link, the sensor power supply and the power supply for the main display module.