Switch Operation
Switches control the operation of the alert indicators and the action alarm. Switches are two-state devices. The two states are Closed switches and Open switches.
Closed Switch - The closed switch connects the control input to frame ground (battery negative).
Open Switch - The open switch does not connect the control input to frame ground (floating input).
During normal operation, all switches are open. Limit switches close when the switches are mechanically activated. Other switches close when the condition of a machine system exceeds the set point of the switch. The closing of a switch completes the circuit. Then, the corresponding alert indicator is illuminated and/or the action alarm sounds.
The illumination of an alert indicator and/or the sounding of the action alarm notifies the operator of an abnormal condition.
Note: Some machines are equipped with other electronic controls that supply the machine monitor with input information in place of a switch. These controls use an electronic circuit to connect the corresponding alert indicator within the machine monitor to ground.
Note: For specifications for the switches, refer to the Service Manual, "Electrical System Schematic".
Transmission Oil Temperature Switch
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| Illustration 1 | g00563651 |
Transmission Oil Temperature Switch | |
During normal operation, the transmission oil temperature switch is open. The switch closes to ground when the transmission oil temperature exceeds the trip point. The closed switch provides a path to ground for the transmission oil temperature indicator and the action alarm.
The illumination of the transmission oil temperature indicator and the sounding of the action alarm notifies the operator that the transmission oil temperature is high.
When the switch is off the machine and on the bench, the switch is in the "normally open" position.
Actuation temperature is 107° ± 3.0°C (225° ± 5.0°F).
Deactuation temperature is a minimum of 98°C (208.0°F).
Differential Lube Pressure Switch
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| Illustration 2 | g00563683 |
Differential Lube Pressure Switch | |
During normal operation, the differential lube pressure switch is open for the contacts (A) and (C) that are used. The switch is closed to ground when the differential lube pressure is less than the trip point. Insufficient oil flow to the differential can cause this low pressure condition. The closed switch provides a path to ground for the indicator for the differential lube and the action alarm.
The illumination of the indicator for the differential lube and the sounding of the action alarm notifies the operator that the oil flow to the differential is low. The differential lube pressure switch is located in the output line of the differentiall pump.
When the switch is off the machine and on the bench, contacts (A) and (C) of the switch are closed. The switch is in the "normally closed" position.
Actuation pressure is a maximum of 90.0 kPa (13.0 psi).
Deactuation pressure is 35 ± 21 kPa (5.0 ± 3.0 psi).
Hydraulic Oil Temperature Switch/Sender
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| Illustration 3 | g00563716 |
Hydraulic Oil Temperature Switch/Sender | |
The hydraulic oil temperature switch/sender is the combination of a switch and a sender in a single device. The switch in the device is used as an input to the machine monitor.
During normal operation, the hydraulic oil temperature switch is open. The switch closes to ground when the hydraulic oil temperature exceeds the trip point. The closed switch provides a path to ground through the machine monitor for only the action alarm. Also at this time, the sender should cause the hydraulic oil temperature gauge to be in the red zone.
The action alarm and the hydraulic oil temperature gauge notifies the operator that the hydraulic oil temperature is high.
When the switch is off the machine and on the bench, the switch is in the "normally open" position.
The specifications that follow are for the Switch:
- Actuation temperature for the switch is 82.0° ± 3.0°C (180.0° ± 5.0°F).
- Deactuation temperature for the switch is a minimum of 74.0°C (165.0°F).
The specifications that follow are for the Sender:
- Resistance of the sender at 50°C (122°F) is 755 to 943 Ohms.
- Resistance of the sender at 82.2°C (180°F) is 124 to 154 Ohms.
Coolant Temperature Switch/Sender
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| Illustration 4 | g00564102 |
Coolant Temperature Switch/Sender | |
The Coolant Temperature Switch/Sender is the combination of a switch and a sender in a single device. The switch in the device is used as an input to the machine monitor.
During normal operation, the coolant temperature switch is open. The switch closes to ground when the engine coolant temperature exceeds the trip point. The closed switch provides a path to ground through the machine monitor for only the action alarm. Also at this time, the sender should cause the engine coolant temperature gauge to be in the red zone.
The action alarm and the engine coolant temperature gauge notifies the operator that the engine coolant temperature is high.
When the switch is off the machine and on the bench, the switch is in the "normally open" position.
The specifications that follow are for the Switch:
- Actuation temperature for the switch is 108.0° ± 3.0°C (226.0° ± 5.4°F).
- Deactuation temperature for the switch is a minimum of 100.0° C (212.0° F).
The specifications that follow are for the Sender:
- Resistance of the sender at 50° C (122° F) is 755 to 943 Ohms.
- Resistance of the sender at 82.2° C (180° F) is 124 to 154 Ohms.
Engine Oil Pressure Switch
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| Illustration 5 | g00564124 |
Engine Oil Pressure Switch | |
During normal operation, the engine oil pressure switch is open. The switch closes to ground when the engine oil pressure is less than the trip point. The closed switch provides a path to ground through the machine monitor only for the action alarm. Also at this time, the sender should cause the engine oil pressure gauge to be in the red zone.
The action alarm and the engine oil pressure gauge notifies the operator that the hydraulic oil temperature is high.
When the switch is off the machine and on the bench, the switch is in the "normally closed" position.
Actuation pressure is a maximum of 80.0 kPa (12.0 psi).
Deactuation pressure is 38.0 ± 10.0 kPa (6.0 ± 1.5 psi).
Steering Filter Bypass Flow Switch
During normal operation, the steering filter bypass flow switch is open. The switch closes to ground when the system oil flow goes around the combined steering/hydraulic filter (bypasses). The closed switch provides a path to ground for the steering filter bypass flow indicator and the action alarm.
The illumination of the steering filter bypass flow indicator and the sounding of the action alarm notifies the operator that the oil is bypassing the combined steering/hydraulic filter.
When the switch is off the machine and on the bench, the switch is in the "normally open" position.
Parking Brake Switch For "C" and "D" Series
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| Illustration 6 | g00564512 |
Parking brake switch for the Challenger Agricultural Tractors ("C" and "D" Series) | |
During normal operation, when the parking brake is not applied the parking brake switch is open. The switch closes to ground when the parking brake is applied. The closed neutral switch and the closed parking brake switch provide a path to ground for the parking brake indicator and the action alarm.
The parking brake indicator and the sounding of the action alarm notifies the operator that the parking brake is applied while the machine is in gear.
When the switch is off the machine and on the bench, the switch is in the "normally closed" position.
Note: On the Challenger 85C Agricultural Tractors, the ground circuit for the parking brake switch goes through a diode assembly before the ground circuit reaches the neutral switch. The diode assembly is used in conjunction with the dual horsepower relay.
Parking Brake Switch For "E" Series
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| Illustration 7 | g00564518 |
Parking brake switch for the Challenger Agricultural Tractors ("E" Series) | |
During normal operation, when the parking brake is not applied the parking brake switch is open. The switch closes to ground when the parking brake is applied. The closed parking brake switch and the closed neutral switch provide a path to ground for the parking brake indicator and the action alarm.
The parking brake indicator and the sounding of the action alarm notifies the operator that the parking brake is applied while the machine is in gear.
When the switch is off the machine and on the bench, contacts (C) and (NO) of the neutral switch are open. The switch is in the "normally open" position.
Note: On the Challenger E Series machines, the parking brake indicator lights whenever the parking brake lever is engaged. The action alarm sounds whenever the parking brake lever is engaged and the transmission control is not in the NEUTRAL position.
Neutral Switch
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| Illustration 8 | g00564518 |
Neutral Switch | |
When the shift lever is in neutral, the neutral switch is open. When the shift lever is moved out of neutral, the neutral switch closes to ground. The closed neutral switch and the closed parking brake switch provide a path to ground for the parking brake indicator and the action alarm.
The illumination of the parking brake indicator and the sounding of the action alarm notifies the operator that the parking brake is applied while the machine is in gear.
When the switch is off the machine and on the bench, contacts (C) and (NO) of the neutral switch are open. The switch is in the "normally open" position.
Note: On the Challenger 85C Agricultural Tractors, the neutral switch also provides a path to ground for the dual horsepower relay.
Running Lamp Switch (Dimmer)
When the dimmer switch is OFF during normal operation, contacts (1) and (2) of the dimmer switch are open. When the dimmer switch is ON with the high beams in operation, contacts (1) and (2) are closed to +battery.
The closed dimmer switch supplies +battery to the alert indicator for high beams at the machine monitor.
Note: In order for the alert indicator for the high beams to light, the ground signal for the high beams at the machine monitor must be connected to machine ground.
Note: On the Challenger E Series machines, the high beam indicator is located separately on the dash. The high beam indicator is not part of the machine monitor.
Turn/Hazard/Horn Switch
When the turn/hazard/horn switch is placed in position for a turn or a hazard, a ground (turn common) is provided to the indicators for the left and right turn signal of the machine monitor. The switch also provides the ground signal that actuates the relays for a left turn or a right turn. These relays then provide a flasher signal to the corresponding indicator of the machine monitor (left or right).