 | |
| Illustration 1 | g03642671 |
Illustration of the electrical connections fro the Governor Control module. | |
The Automatic Engine Speed Control reduces the engine speed while the machine is inactive. The Automatic Engine Speed Control raises the engine speed from idle to the engine speed dial setting when a machine function is detected.
Note: When troubleshooting the electrical components on the machine refer to the electrical schematic in SIS matching your machine.
The AEC module monitors two pressure switches and the engine speed dial for increased demand for engine speed.
The machine monitor is connected to the AEC module by wire N933-PU. The monitor will display the operating condition of the AEC module. When the AEC module is not operating correctly, there are three inputs that could cause a failure of the module. The AEC module receives input from the speed dial, and two pressure switches. The AEC module is powered by the main battery through a 15 A fuse.
The first step in troubleshooting the AEC module is to locate the fuse for the module on the main fuse panel. Refer to the film on the rear of the fuse panel cover to identify the appropriate fuse. Remove the fuse from the panel and use a multimeter that is set to check the resistance across the fuse. If the fuse is open, replace the fuse and operate the machine. If the fuse opens while testing the operation of the machine, wire 130-GN in the wiring harness should be checked for a short circuit. To confirm a short circuit, a temporary replacement wire should be run from the fuse panel to the module. If a short circuit does not occur when using the temporary wire, then an examination of the existing wiring harness is required. Examine the wiring harness for damage, chaffing, or sharp bends that would indicate possible locations for the short circuit. Repair or, if necessary, replace the wiring harness.
The AEC module is also dependent on input from pressure switches for determining the demand for increased engine speed. The pressure switches monitoring hydraulic demand are the Implement Pressure switch (Pressure Switch A) and the Travel Pressure switch (Pressure Switch B). Both of these switches are normally in the OPEN position. Disconnect each of the switches from the wiring harness. With the switch disconnected, use a multimeter that is set to resistance, and check the resistance across the switch. If the switch is operating correctly, the multimeter should read OPEN.
If the pressure switch is correct, check the wiring harness for the switch. Disconnect the wiring harness at the AEC module and place a jumper wire across pins 2 and 3 of the connector wiring harness. Use a multimeter to check the resistance at the connector for the pressure switch. The resistance measure should be less than 5 ohms. Remove the jumper wire and check the resistance of the circuit again at the connector for the pressure switch. This measurement should reveal that the circuit is open, if the circuit is correct. Repeat this process for Implement Pressure switch. Connect the jumper wire across pins 3 and 8 to check the continuity of this circuit. If the resistance remains low after the jumper wire is removed, check the harness for a short circuit. Locations where chaffing or sharp bends occur in the wiring harness indicate potential short circuit problems. Repair or replace the wiring harness as needed.
If the switch wiring harness and switches are operating correctly, reconnect the pressure switches to the wiring harness.
The Speed Dial is the final input to the AEC module. To check the function of the Speed Dial, at the AEC module remove the signal wire (wire P969-BR) for the Speed dial from the harness connector. Leave the 5 VDC supply wire and ground wire for the circuit connected to the AEC module. Use a voltage meter set to display VDC and connect the positive lead of the meter to the signal wire. Connect the negative lead of the meter to a clean ground source on the frame. Start the machine. Set the Speed Dial to a low idle setting, the meter should read 1.8 ± 0.15 VDC. Set the Speed Dial to a high idle setting, the meter should read 4.55 ± 0.1 VDC. If the Speed Dial signals are correct, reconnect the signal wire to the AEC connector. If the signal from the Speed Dial is not correct, check the continuity of the signal wire. Connect one end of the wire to a ground location and check the continuity of the wire. If the signal wire is operating correctly, check the power and ground connectors to the Speed Dial. Disconnect the Speed Dial from the circuit and check the voltage between Pin 1 (wire P997-OR) and Pin 2 (wire H742-PU) of the dial connector. The voltage reading should be 5 VDC. If the voltage is not correct, check the voltage at pins 4 (red wire) and 5 (pink wire) of the AEC module. If the voltage is not correct at the AEC module, the module must be replaced. If the voltage is correct at the module, the wiring harness must be inspected for damage. Repair or replace the wiring harness as needed. If there is not 12 VDC, replace the AEC module.
During normal operation, the AEC module will have 12 VDC across pins 1 and 2 on the six pin connector. Set the multimeter to display VDC and connect the positive lead of the meter to Pin 1. Connect the negative lead of the meter to Pin 2. The voltage should read 12 VDC on the display of the multimeter. The 12 VDC signal will be intermittent when the speed dial is adjusted.
If Pin 1 and Pin 2 on the AEC module has 12 VDC, check the voltage between Pin 5 and Pin 6 of the engine governor actuator. If there is 12 VDC, then the circuit is good. If voltage between Pin 5 and Pin 6 does not have 12 VDC, temporary replacement wires should be run from the governor controller to the engine governor actuator. This action bypasses wire H740-OR and wire H741-WH. Recheck for 12 VDC between Pins 1 and 2 on the engine governor actuator. If there is 12 VDC when using the temporary wires, then an examination of the existing wiring harness is required. Examine the wiring harness for damage, chaffing, or sharp bends that would indicate possible locations for the open circuit. Repair or, if necessary, replace the wiring harness. If the multimeter does not show 12 VDC after the temporary wires, replace the engine governor actuator.
Pin 2 of the six Pin connector on the AEC module, will have an intermittent 12 VDC signal when the speed dial is adjusted. Set the multimeter to display VDC and connect the positive lead of the meter to Pin 2. Connect the negative lead of the meter to a clean ground source on the frame. The voltage should intermittently read 12 VDC on the display of the multimeter while adjusting the speed dial. If Pin 2 does not have this signal, replace the AEC module.
If Pin 2 has this signal, check Pin 6 of the engine governor actuator connector. If there is no voltage present, then a temporary replacement wire should be run from the governor controller to the engine governor actuator. Check for the intermittent 12 VDC signal on Pin 6 on the engine governor actuator. If there is 12 VDC when using the temporary wire, then an examination of the existing wiring harness is required. Examine the wiring harness for damage, chaffing, or sharp bends that would indicate possible locations for the open circuit. Repair or, if necessary, replace the wiring harness. If voltage is not present after the temporary wire, then replace the engine governor actuator.
Pin 3 on the six pin AEC connector will have 5 VDC when the key is on. If there is no voltage present, check the fuse for an open. If the fuse is found to be good and the ground for the AEC module is good, replace the AEC module. If there is 5 VDC at pin 3, check for voltage at Pin 1 of the engine governor actuator. If there is 5 VDC, then the circuit if working correctly. If there is no voltage present, then use a temporary wire to bypass wire M729-PU between Pin 3 of the AEC module and Pin 1 of the engine governor actuator. If there is 5 VDC when using the temporary wire, then an examination of the existing wiring harness is required. Examine the wiring harness for damage, chaffing, or sharp bends that would indicate possible locations for the open circuit. Repair or, if necessary, replace the wiring harness.
Pin 5 will have the same voltage as the dial switch signal wire (wire P969-BR). If Pin 5 of the six pin AEC connector does not have the same voltage as the dial switch signal wire of the AEC 8 pin connector, replace the AEC module. If Pin 5 does have the same voltage, then check Pin 2 on the engine governor actuator connector. If the voltage is not the same as the dial switch signal wire, then use a temporary wire to bypass wire M730-YL between Pin 5 of the AEC module and Pin 2 of the engine governor actuator. If the signal is the same voltage as the dial switch signal when using the temporary wire, then an examination of the existing wiring harness is required. Examine the wiring harness for damage, chaffing, or sharp bends that would indicate possible locations for the open/ high resistance circuit. Repair or, if necessary, replace the wiring harness.
If none of the tests described above reveal a problem, replace the AEC module. After replacement of the module, test the machine to insure the problem has been resolved.