Switches provide an open, a ground or a +battery signal to the switch inputs of the VIMS modules. A switch can be open or a switch can be closed.
- When a switch is open, no signal is provided to the corresponding input of the VIMS modules. The condition of no signal is also called "floating".
- When a switch is closed, the ground or +battery signals are provided to the corresponding inputs of the VIMS modules.
| |
| Illustration 1 | g00482124 |
|
Oil Level Switch ("Engine, Hydraulic") (1) Switch (2) Schematic symbol | |
Oil level switch (1) is closed to ground during normal operation. The switch opens when the oil level is less than the minimum level. When the switch opens the VIMS module warns the machine operator of the low oil level. When the switch is tested on the bench, the switch is open. The float is in the DOWN position.
Pump Inlet Valve Switch (LHEX)
| |
| Illustration 2 | g00482127 |
|
Pump Inlet Valve Limit Switch (1) Switch (2) Schematic symbol | |
Switch (1) is attached to the control handle of the inlet suction line valve for each pump. The valves are located at the hydraulic tank. When the inlet valve of the pump is open the switch is closed. The closed switch grounds the signal circuit. When the inlet valve of the pump is closed, the switch opens the signal circuit. A machine could use multiple pump inlet valve switches that are wired in series. If any of the pump inlet valve switches are open, the VIMS module warns the operator that the inlet valve of the pump is closed. When the switch is tested on the bench, the switch is open. The normally closed contacts are not used in this application.
| |
| Illustration 3 | g00482136 |
|
Chip Detector Switch (1) Schematic symbol. (2) Switch. | |
During normal operation, switch (2) is open. The switch contacts are magnetic in order to attract metal particles. The switch closes the signal circuit to ground, when enough metal chips cover the switch contacts in order to complete the circuit. The VIMS module warns the operator that chips have been detected when the switch is closed. When the switch is tested on the bench, the switch is open. No metal objects are covering the contacts of the switch. The switch is considered closed, when the resistance is between approximately 0 and 2000 ohms.
| |
| Illustration 4 | g00482137 |
|
Steering Flow Switches (1) Schematic symbol (2) Switch | |
During normal operation, steering flow switch (2) is closed to ground. The switch opens when the oil flow in the steering system is less than the specified limit. The VIMS module warns the operator that the oil flow of the steering systems is low when the switch is open. Switch (2) is used in the primary steering systems and the supplemental steering systems. When the switch is tested on the bench, the switch is open.
| |
| Illustration 5 | g00482139 |
|
Filter Bypass Switch (1) Switch (2) Schematic symbol | |
Filter bypass switch (1) has a plunger within the switch that closes the contacts with an acceptable pressure drop across the filter. The switch closes the signal circuit to ground during normal operation. When the pressure across the filter is greater than the specified limit the switch plunger moves in order to allow the switch contacts to open. The VIMS module will warn the operator that the filter is restricted when the switch is open. When the switch is tested on the bench, the switch is open.
Note: The VIMS module takes the fluid temperature into consideration before warning the operator. Cold fluid has a higher viscosity which causes a higher differential pressure across the filter than fluid at normal operating temperature. When the fluid temperature is below a specified limit, the filter bypass event is ignored by the VIMS module. The temperature inhibit is not used with the fuel filter.
| |
| Illustration 6 | g00482160 |
|
Differential Pressure Switch (1) Switch (2) Typical schematic symbol (3) Filter inlet port (4) Filter outlet port | |
Differential pressure switch (1) is activated by a pressure difference between the filter inlet port (3) and filter outlet port (4). The switch contacts are held closed by a spring inside the switch during normal operation. When the pressure at filter inlet port (3) exceeds the pressure at filter outlet port (4) by a specified amount, the force of the spring is overcome and the switch contacts are opened. The VIMS module will warn the operator that the filter is restricted when the switch is open. When the switch is tested on the bench, the switch is closed because there is no pressure difference between ports (3) and (4).
| |
| Illustration 7 | g00482162 |
|
Coolant Flow Switch (1) Switch (2) Schematic symbol | |
During normal operation, coolant flow switch (1) is closed to ground as coolant flows against the paddle. The switch opens when coolant flow is less than the specified limit. The VIMS module warns the operator of the low coolant flow in the engine cooling system when the switch is open. When the switch is tested on the bench, the switch is open.
| |
| Illustration 8 | g00482164 |
|
Steering Pressure Switch (1) Schematic symbol (2) Switch | |
During normal operation, steering pressure switch (1) is closed to ground. When the pressure of the steering system is less than the specified limit, the switch is open. When the pressure of the steering system is greater than the specified limit, the switch is closed. When the switch is being tested on the bench, contact B and contact C of the switch are closed. When the switch is tested on the bench, the switch contacts A and Bare open. The normally closed contacts (B and C) are not used in this application.
Automatic Lubrication Grease Level Switch (LWL)
| |
| Illustration 9 | g00527779 |
|
Automatic Lubrication Grease Level Switch (1) Switch (2) Schematic Symbol | |
The level of the auto lube lubricant is monitored by the VIMS on the 994D. When the level of lubricant in the tank becomes low, level switch (1) will open. This causes the VIMS to display a warning on the message center.