3618 Engine Caterpillar

A frequency generator is used to simulate the signal from the engine speed sensor. The frequency represents the engine rpm. This procedure checks the operation of the speed switch's crank terminate relay, oil step relay, and overspeed relay. The setpoints for the speed switch are adjusted, if necessary.

1. Turn OFF the power to the monitoring system.

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Illustration 1	g00872329
(1) Cover screw for the "OVERSPEED" potentiometer (2) Cover screw for the "CRANK TERM" potentiometer (3) Cover screw for the "OIL STEP" potentiometer (4) Retainer clip (5) "OVERSPEED" indicator (6) "RESET" switch

2. To gain access to the potentiometers, remove cover screws (1), (2), and (3) .

3. Connect the positive "+" lead from a source of 24 VDC to "8-40 VDC" terminal 6. Connect the negative "-" lead to "8-40 VDC" terminal 5.

4. Connect the frequency generator's positive "+" lead to "PICK-UP SIG" terminal 4. Connect the negative "-" lead to "PICK-UP SHLD COM" terminal 3.

5. Turn ON the 24 VDC for the speed switch.

6. Adjust the speed switch's crank terminate relay.

   1. Connect the 9U-7330 Digital Multimeter to "CRANK TERM NO" terminal 10 and "CRANK TERM COM" terminal 11. Set the multimeter to the "Ohms" scale.

   2. Turn ON the power to the frequency generator.

   3. Adjust the frequency generator to 0 Hz.

   4. Adjust the frequency to 691 Hz.

   5. Slowly increase the frequency in increments of 1 Hz and observe the resistance between terminals 10 and 11. Continue to increase the frequency in 1 Hz increments until the frequency is 701 Hz.

      Note: A frequency of 701 Hz corresponds to the setpoint for the crank terminate speed of 165 rpm.

      Expected Result

      The resistance became less than 5 ohms at a frequency of 701 Hz. The circuit is closed and the crank terminate relay is operating correctly.

      Results

      OK - The resistance became less than 5 ohms at a frequency of 701 Hz. The circuit is closed and the crank terminate relay is operating correctly. Proceed to Step 7.

      Not OK - The resistance became less than 5 ohms at a frequency of less than 701 Hz (165 rpm). The crank terminate relay was energized too soon. The setpoint is too low and the setpoint must be adjusted. To reset the relay, turn OFF the power to the speed switch. Use the 4C-4029 Adjustment Tool to turn potentiometer (2) clockwise for two full turns (720 degrees). Continue to provide a frequency of 701 Hz. Turn ON the power to the speed switch and slowly turn potentiometer (2) counterclockwise until the resistance is less than 5 ohms. Then turn OFF the power to the speed switch. Adjust the frequency generator to 0 Hz. Turn ON the power to the speed switch. Repeat Steps 6.d and 6.e until the resistance becomes less than 5 ohms at a frequency of 701 Hz.

      Not OK - The resistance is greater than 20,000 ohms or out of range at a frequency of 701 Hz (165 rpm). The crank terminate relay did not energize. The setpoint is too high and the setpoint must be adjusted. Continue to provide a frequency of 701 Hz and use the 4C-4029 Adjustment Tool to slowly turn potentiometer (2) counterclockwise until the resistance is less than 5 ohms. Adjust the frequency generator to 0 Hz. To reset the relay, turn OFF the power to the speed switch and wait for at least two seconds before you turn ON the power again. Repeat Steps 6.d and 6.e until the resistance becomes less than 5 ohms at a frequency of 701 Hz.

7. Disconnect the ohmmeter from terminals 10 and 11. Install cover screw (2). Tighten the screw to a torque of 0.20 ± 0.03 N·m (2.000 ± 0.300 lb in).

8. Adjust the speed switch's oil step relay.

   1. Connect an ohmmeter to normally open terminals 13 and 14.

   2. Adjust the frequency generator to 0 Hz. Then adjust the frequency to 3339 Hz.

   3. Observe the LED in the port for potentiometer (3) and slowly increase the frequency in increments of 1 Hz until the frequency is 3349 Hz. Observe the LED and observe the ohmmeter.

      Note: A frequency of 3349 Hz corresponds to the setpoint for the oil step speed of 788 rpm.

      Expected Result

      The LED illuminated at a frequency of 3349 Hz (788 rpm). At nine seconds after the LED illuminated, the ohmmeter reading was less than 5 ohms. The oil step relay is operating correctly. Remove the ohmmeter.

      Results

      OK - The LED illuminated at a frequency of 3349 Hz (788 rpm). At nine seconds after the LED illuminated, the ohmmeter reading was less than 5 ohms. The oil step relay is operating correctly. Proceed to Step 9.

      Not OK - The LED illuminated before reaching a frequency of 3349 Hz (788 rpm). The oil step relay was energized too soon. The setpoint is too low and the setpoint must be adjusted. Turn potentiometer (3) clockwise until the LED is extinguished. Continue to provide a frequency of 3349 Hz and slowly turn potentiometer (3) counterclockwise until the LED illuminates. Repeat Steps 8.b and 8.c until the LED illuminates at a frequency of 3349 Hz. Verify that the ohmmeter reads less than 5 ohms at nine seconds after the LED illuminates.

      Not OK - The LED did not illuminate at a frequency of 3349 Hz (788 rpm). The oil step relay did not energize. The setpoint is too high and the setpoint must be adjusted. Slowly turn potentiometer (3) counterclockwise until the LED illuminates. Repeat Steps 8.b and 8.c until the LED illuminates at a frequency of 3349 Hz. Verify that the ohmmeter reads less than 5 ohms at nine seconds after the LED illuminates.

9. Install cover screw (3). Tighten the screw to a torque of 0.20 ± 0.03 N·m (2.000 ± 0.300 lb in).

10. Adjust the speed switch's overspeed relay.

    1. Adjust the frequency generator to 0 Hz.

    2. Adjust the frequency to 5033 Hz.

    3. Slowly increase the frequency in increments of 1 Hz and observe "OVERSPEED" indicator (5). Continue to observe the "OVERSPEED" indicator and increase the frequency in 1 Hz increments until the frequency is 5043 Hz.

       Note: A frequency of 5043 Hz corresponds to the setpoint for the overspeed shutdown of 1187 rpm.

       Expected Result

       The "OVERSPEED" indicator illuminated at a frequency of 5043 Hz (1187 rpm). The overspeed relay is operating correctly.

       Results

       OK - The "OVERSPEED" indicator illuminated at a frequency of 5043 Hz (1187 rpm). The overspeed relay is operating correctly. Proceed to Step 11.

       Not OK - The "OVERSPEED" indicator illuminated before reaching a frequency of 5043 Hz (1187 rpm). The relay was energized too soon. The setpoint is too low and the setpoint must be adjusted. Turn potentiometer (1) clockwise for two full turns (720 degrees). Press "RESET" switch (6). Continue to provide a frequency of 5043 Hz and slowly turn potentiometer (1) counterclockwise until the "OVERSPEED" indicator illuminates. Adjust the frequency to 0 Hz and press the "RESET" switch again. Repeat Steps 10.b and 10.c until the "OVERSPEED" indicator illuminates at a frequency of 5043 Hz (1187 rpm).

       Not OK - The "OVERSPEED" indicator did not illuminate at a frequency of 5043 Hz (1187 rpm). The overspeed relay was not energized. The setpoint is too high and the setpoint must be adjusted. Continue to provide a frequency of 5043 Hz and slowly turn potentiometer (1) counterclockwise until the "OVERSPEED" indicator illuminates. Adjust the frequency to 0 Hz and press "RESET" switch (6). Repeat Steps 10.b and 10.c until the "OVERSPEED" indicator illuminates at a frequency of 5043 Hz (1187 rpm).

11. Turn OFF the 24 VDC for the speed switch. Disconnect the leads of the 24 VDC.

12. Turn OFF the power to the frequency generator and remove the frequency generator. Press "RESET" switch (6) .

13. Install cover screw (1). Tighten the screw to a torque of 0.20 ± 0.03 N·m (2.000 ± 0.300 lb in). Disconnect the frequency generator.

14. Verify that the overspeed shutdown is operating correctly. Refer to Testing and Adjusting, "Engine Speed Switch - Test".

15. Record the information from Table 2 on a tag. Attach the tag to the speed switch.
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    Table 2

    Parameters and Setpoints for the Speed Switch
    Parameter	Setpoints
    	Engine RPM	Frequency
    Crank terminate speed	165	701 Hz
    Oil step speed	788	3349 Hz
    Overspeed	1187	5043 Hz

16. Install a lockwire through cover screws (1), (2), and (3). Thread the lockwire through retainer clip (4) and seal the lockwire.