Switches
Switches provide information to the ECM. Switches are two state devices. The switches are either open or the switches are closed.
Closed - The switch closes the circuit to ground or the switch closes the circuit to the battery.
Open - the switch opens a circuit to the ECM input.
Key Start Switch
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| Illustration 1 | g00927534 |
When the key start switch is in the ON position, electrical power from the batteries is supplied to the electronic control modules.
When the key start switch is in the START position and the conditions for starting the engine are satisfied, the start relay is energized.
Transmission Lock Switch
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| Illustration 2 | g01230290 |
When the transmission disable switch is in the locked position, the transmission will be locked (neutralized). In the unlocked position, the transmission will be unlocked (enabled).
If the transmission disable switch is placed in the locked position while the transmission is in neutral, direction shifts out of neutral are inhibited. If the transmission disable switch is set to the locked (neutralized) position while the transmission is in any forward or reverse speed range, the transmission is shifted to neutral. The transmission will remain in neutral until the operator moves the shifter into neutral and out of neutral into forward or reverse after the transmission disable switch is placed in the unlocked (enabled) position.
Conversely, if the transmission disable switch is set to the unlocked (enabled) position, the operator will have full control over the transmission.
Auto/Manual Shift Switch
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| Illustration 3 | g01230321 |
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| Illustration 4 | g01245023 |
The Autoshift transmission shall provide two modes of operation that are operator selectable. The modes of operation are described below.
The control system automatically selects the transmission gear when the machine is in the selected Autoshift mode. In response to the transmission output speed, this provides the most efficient machine operation within the operator selected maximum gear limit. The maximum gear limit is set by the twist grip on the shift lever. If the maximum Forward Gear is configured as 5 then Fifth gear can be reached by placing the shift lever in the Fourth gear position and achieving the Fifth gear upshift point while in Autoshift mode. The transmission will only shift automatically down to Second gear by default. If the First Gear Autoshift Enable Status parameter is configured as First Gear Enabled in Caterpillar Electronic Technician (ET), then the system will automatically downshift all the way down to First gear. In this mode the downshift / neutralizer switch must be used to downshift to First gear. In autoshift mode, a downshift is allowed in any gear. The transmission will remain in the new gear for a minimum of 5 seconds. The control will monitor the autoshift point in order to determine when to upshift to the next gear.
When in Manual mode, the transmission is placed in the gear (1-4) selected by the operator through the column mounted twist grip regardless of machine ground speed. Fifth gear is not selectable when in the manual mode. In manual mode, the transmission downshift / neutralizer switch does not allow any downshifts. The transmission system shall provide configurable parameters for transmission type. Transmission type enables the ECM to properly diagnose system faults. This information will be configurable in the machine control via ET.
Implement Disable Switch
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| Illustration 5 | g01230308 |
The implement disable switch disables the pilot hydraulics and electro-hydraulics on the machine with signals to the Machine ECM. When the top of the switch is pressed, implements function normally. When the bottom of the implement disable switch is pressed, implements are disabled.
Loader Quick Coupler Pins Switch
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| Illustration 6 | g01230677 |
A rocker switch is used to activate this function. This is a spring centered switch and momentary in either direction. The lower side of the switch is pressed in order to engage the coupler pins. The upper side of the switch is pressed in order to disengage the pins. Additionally, there is a red slide on the switch that must be pulled down before the switch can be rocked upward. The hydraulic operation is engaged by the front coupler pins which are driven by a double acting hydraulic cylinder. Hydraulic flow for quick coupler is directed to the cylinder from the front auxiliary hydraulic circuit, via a 2-position, 6-way solenoid operated valve. The solenoid valve is spring loaded in the position that directs flow to the normal auxiliary circuit.
When the operator moves the coupler switch to engage or disengage the coupler pins, the following should occur:
- Turn off the continuous auxiliary function, if on.
- Energize the diverter valve, to direct flow to the quick coupler cylinder.
- Activate the auxiliary function, in one direction in order to engage the pins or the opposite direction in order to disengage, to 30 percent command.
Note: The command value should be adjustable by engineers during PD, to be a set value in production.
When the coupler switch is then centered:
- Neutralize the auxiliary circuit.
- De-energize the diverter solenoid.
- DO NOT engage again the continuous flow auxiliary automatically.
- Require that the auxiliary slider be centered before reacting to any input on this function
Continuous Flow Switch
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| Illustration 7 | g01230321 |
The auxiliary hydraulics system will allow a request from the operator for continuous flow of the system. The operator is not required to maintain activation of the auxiliary hydraulics input. To activate continuous flow, the operator will actuate the auxiliary hydraulic circuit in order to obtain the desired flow rate. Once the operator has obtained the desired flow rate, the momentary continuous flow switch should be actuated and released in order to provide a switch to ground input to the ECM. The operator can then release the auxiliary hydraulics actuator and the flow rate will remain on. The operator must actuate one of the following in order to turn continuous flow off:
- a front auxiliary hydraulics input on the joystick handle
- the quick coupler switch
- the implement disable switch
- the continuous flow switch
Diagnostics will be performed on the continuous flow switch when the installation configuration is set to INSTALLED.
Boosted Brake Pressure Switch
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| Illustration 8 | g01443907 |
The pressure switch will warn the operator when the brake oil pressure drops below the deactuation pressure of the pressure switch.
When the sensing device provides a ground signal to the LED panel and the ECM indicating the brake fluid pressure is low, the indicator on the LED panel will be illuminated. If the engine is running when this occurs, a Level 3 warning shall be issued and an event logged. If the engine is not running when this occurs, then only a Level 1 warning shall be issued and no event shall be logged.
Air Filter Switch
When a grounded input signal is received into the ECM indicating that the air filter restriction switch has been activated the indicator will be turned on. After a 5 minute debounce, a Level 1 event will be logged.
Coolant Temperature Switch
This Level 2 event is logged when the temperature is hot enough to activate the engine coolant temperature switch (greater than 113 °C (235 °F)) for 3 seconds.
The engine coolant temperature shall be read into the engine coolant temperature gauge. The range of values on the gauge shall be from 49 °C (120 °F)to 127 °C (261 °F) with a red line indication at 113 °C (235 °F) and the normal range defined by a mark at 88 °C (190 °F).
Hydraulic Oil Filter Bypass Switch
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| Illustration 9 | g01230565 |
This Level 1 event is logged when the Hydraulic Oil Filter Bypass is detected and the hydraulic oil temperature is greater than 42 °C (108 °F)for a debounce time of 10 seconds.
The pressure switch has a plunger inside the switch that closes the contacts with an acceptable pressure drop across the screen. The pressure switch grounds the signal circuit during normal operation. The pressure switch plunger moves in order to allow the pressure switch contacts to open. The pressure switch contacts open when pressure across the screen is greater than the specified value. If the screen is restricted the open pressure switch sends a signal to the ECM. The ECM informs the operator that the screen is restricted or dirty. The normal state of a pressure switch that is not installed is normally open. With a PSI between 40 to 44 PSI, the switch will remain closed. When the PSI is at 30 PSI as a minimum, the switch will remain open. The circuit for the switch is normally open. The bypass valve will open in order to protect the system if the filter is restricted. The bypass switch provides an input signal to the ECM. The ECM determines if the filter is restricted and the ECM informs the Caterpillar Electronic Technician.
Engine Oil Pressure Switch
This Level 3 event is logged when the engine oil pressure is low enough to activate the engine oil pressure switch for 3 seconds and the engine is detected to be running (Engine speed => 400 RPM). If the engine is not running (Engine speed less than 400 RPM) then this shall be displayed as a Level 1 event but not logged. The signal contact for the engine oil pressure switch connects to the ECM at contact J2-28.
This switch is a pushbutton switch that monitors the output of the engine oil. The pressure switch will warn the operator when the oil pressure in the engine drops below the deactuation pressure of the pressure switch.
Transmission Neutralizer Switch
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| Illustration 10 | g00581331 |
The purpose of this feature is to allow the operator to quickly and easily downshift or temporarily neutralize the Autoshift transmission. The neutralizer switch is used to both downshift the transmission and to neutralize the transmission. The transmission is neutralized while the switch is held. If the switch is held for less than 1.2 seconds and then released, the transmission is downshifted one gear.
Downshift Function
The downshift function is requested when the neutralizer switch is pressed and released within 1.2 seconds. When this occurs, the transmission downshifts one gear and remains in that gear for 5 seconds. After 5 seconds, normal autoshift operation resumes (if autoshift is enabled). Normal autoshift operation may resume before the 5 seconds has expired if a speed or direction change occurs. Multiple downshift commands can be queued up, though the machine will not downshift until the machine is below the maximum speed for the next lower gear. The 5 second delay does not apply here as the speed inhibits will provide adequate delays between downshifts. If the neutralizer switch is held for longer than 1.2 seconds, no downshift command is given. If the transmission is in First gear when a downshift command is issued, the command shall be ignored. If the shift lever is in position 2, the downshift button will force the machine to be downshifted immediately and held in First gear for at least 5 seconds, or until a speed or direction change occurs. After 5 seconds, normal autoshift operation resumes (if autoshift is enabled). If the switch is held continuously for longer than 3 minutes, a level 2 diagnostic code (CID 0629 - FMI 04) will be logged. Upon the diagnostic code being cleared the transmission shall remain neutralized until the shift lever is cycled to neutral and back to a valid gear.
Neutralizer Function
The operator may momentarily neutralize the transmission by pressing the neutralizer switch. While the switch is held, the transmission is neutralized. The transmission returns to the previous gear when the neutralizer switch is released, or to a lower gear if the switch is released within 1.2 seconds. Disengaging the directional clutch neutralizes the transmission, and the speed clutch remains engaged. This improves shift speed when the transmission is put back into gear. Normal autoshift operation may resume before the 5 seconds has expired if a speed or direction change occurs. If the switch is held continuously for longer than 3 minutes, a level 2 diagnostic code (CID 0629 - FMI 04) will be logged. Upon the diagnostic code being cleared the transmission shall remain neutralized until the shift lever is cycled to neutral and back to a valid gear.
Ride Control Switch
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| Illustration 11 | g01230329 |
A three-position switch enables Ride control. In the held middle OFF position, the ride control function is disabled. The Ride Control function is held-on when the switch is in the ON position. In the held AUTO position, the ride control function activates the ride control solenoid valve when the ground speed is greater than a set limit. The ride control solenoid valve is deactivated when the ground speed is at least 1 km/h less than the set limit. The default set limit for AUTO is 9 km/h. Caterpillar Electronic Technician (ET) will be used to change the set limit. (In summary, in the ON position ride control is enabled, in the OFF position ride control is disabled, in the AUTO position ride control depends on the ground speed.) For the purpose of calculating ground speed a nominal tire radius of 635 mm (25 inch) shall be used.
A pressure switch is placed in series with the ride control relay that controls the solenoid such that when there is pressure on the rod end of the lift cylinder the solenoid driver circuit is open circuited. This prevents ride control from being engaged when there is a load on the rod end such as when the loader is being used as a stabilizer. This and the fact that we are using a relay driver prevents diagnostics from being performed on the ride control solenoid circuit.
A pressure switch is placed in series with the ride control relay that controls the solenoid. When there is pressure on the rod end of the lift cylinder the circuit of the solenoid driver circuit is open. This prevents ride control from being engaged when there is a load on the rod end such as when the loader is being used as a stabilizer. Also, the relay driver prevents diagnostics from being performed on the ride control solenoid circuit.
Note: Whenever the ride control solenoid is activated, the loader lock bypass solenoid (if installed) must also be activated so that lift arm motion can occur.
Parking Brake Switch
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| Illustration 12 | g00726668 |
When the parking brake is engaged the transmission will not shift out of neutral into gear. If the transmission is in forward or reverse when the parking brake is set, the ECM will shift the transmission to neutral. When the operator releases the parking brake the transmission will not engage a directional clutch until the operator selects neutral and then forward or reverse. The ability to double shift the gear selector and drive through the parking brake will still be provided for drive train service procedures.
Sensors
Speed Sensors
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| Illustration 13 | g00909584 |
The transmission is equipped with the following speed sensor:
- XMSN output speed sensor
The transmission output speed sensor is located on the right side of the transmission case. As the gear teeth pass the end of the sensor, an AC voltage is produced. The frequency of the voltage is proportional to the speed of the gear teeth. The ECM uses this signal to make decisions.
Temperature Sensors
Hydraulic Oil Temperature Sensor
The hydraulic oil temperature sensor monitors the temperature of the hydraulic oil. The high hydraulic oil temperature indicator will be supported by an input into the ECM. This will result in the indicator being turned on and a level 2 event being logged whenever the temperature sensor reaches 100°C by the ECM providing a ground signal to the input on the LED panel.
Torque Converter Temperature Sensor
The torque converter temperature sensor monitors the temperature of the torque converter oil. The torque converter temperature sensor is mounted on top of the transmission on the torque converter housing. The torque converter temperature shall be read into the torque converter temperature gauge. The range of values on the gauge shall be from 25°C to 150°C with a red line indication at 121° C and the normal range defined by a mark at 100°C.
Other Inputs
The machine ECM also receives information from the service connector via the Cat Data Link, and the engine ECM via the CAN data link.