3500B Engines for Caterpillar Built Power Modules with the ADEM 2 Electronic Control Module Caterpillar

The engine speed control is used to provide a throttle signal and droop signal to the engine control. The output for rated speed is a pulse width modulated signal. The signal varies with the position of the speed adjust potentiometer. The output for droop is a pulse width modulated signal. The signal varies with the position of the droop adjust potentiometer. The output signal is expressed as a percentage between 0 and 100 percent for the speed adjust potentiometer and between 0 and 10 percent for the droop adjust potentiometer.

The ECM calculates the desired engine rpm. The desired engine rpm is produced by the signal from the rated speed setting and the droop signal. The rated speed signal is valid when the duty cycle is in the range of 5 to 95 percent. If the rated speed signal is invalid, the engine will be set to the low idle.

The droop signal is valid when the duty cycle is in the range of 15 to 85 percent. If the droop signal is invalid, the engine will run with NO droop.

Some applications may choose not to use the speed control. Some applications may use a load sharing unit. The unit is configured to provide the engine control with a rated speed signal. Some of these units can not provide a signal until the engine is running. In these cases, troubleshooting should be performed while the engine is running.

Illustration 1	g00631341

Test Step 1. Inspecting Electrical Connectors

1. Verify that the circuit breakers are not tripped.

2. Turn the circuit breaker at the battery to the OFF position.

3. Turn the ECS to the OFF/RESET position.

4. Check the components and wiring for the following problems: damage, corrosion, abrasion and incorrect attachment

Expected Result:

The components and wiring should be free of the following problems: damage, corrosion, abrasion and incorrect attachment.

Results:

• OK - Proceed to test step 2.

• Not OK -

  Repair: Repair the connectors and/or wiring or replace the connectors and/or wiring.

  Stop.

Test Step 2. Check the Voltage.

1. Turn the circuit breaker at the battery to the ON position.

2. Connect the black probe of the multimeter to the +Battery terminal of the Speed Control. Connect the red probe of the multimeter to the -Battery terminal of the Speed Control.

Expected Result:

The voltage should be 24 ± 5 VDC.

Results:

• OK - The voltage supply to the Speed Control is correct. Proceed to test step 3.

• Not OK -

  Repair: The voltage is not correct. There is a problem with the supply voltage to the Speed Control.

  Stop.

Test Step 3. Determine the Component that has Failed.

1. Determine if the problem is with the input for the throttle or the Droop.

2. Select "UNSURE" if the source of the problem is unknown.

Expected Result:

Results:

• RATED SPEED - Proceed to test step 4.

• DROOP SPEED - Proceed to test step 5.

• Unsure - Proceed to test step 4.

Test Step 4. Check the Throttle Position.

1. Turn the ECS to the STOP position.

2. Observe the position of the throttle on the ET.

3. Turn the Speed Adjust Potentiometer to the lowest setting.
   • 60 Hz equals 1369 RPM

   • 50 Hz equals 1141 RPM

4. Start at the low idle position. Slowly turn the Speed Adjust Potentiometer in the other direction. Monitor the position of the throttle on the ET.

Expected Result:

The Throttle Position on the ET should read 0 percent at the lowest setting and 0 to 100 percent as the Speed Adjust Potentiometer is adjusted.

Results:

• OK - The Speed Control is operating correctly. Stop.

• Not OK - Proceed to test step 6.

Test Step 5. Check the Droop.

1. Turn the ECS to the STOP position.

2. Observe the Droop on the ET.

3. Turn the Droop Adjust Potentiometer in a counterclockwise direction.

4. Slowly turn the Droop Adjust Potentiometer in a clockwise direction. Monitor the Droop on the ET.

   Note: Do not overturn the Droop Adjust Potentiometer in the clockwise direction. The signal will become erratic.

Expected Result:

The Droop on the ET should read 0 percent at the lowest setting and 0 to 10 percent as the Potentiometer is adjusted.

Results:

• OK - The Droop is operating correctly. Stop.

• Not OK - Proceed to test step 7.

Test Step 6. Check the Speed Control.

1. Remove the wire from the S terminal at the Speed Control.

2. Set the multimeter to "VDC". Press the "Hz" button twice so that the % symbol is displayed.

3. Place one probe of the multimeter on the S terminal of the Speed Control. Place the other probe on the -Battery terminal of the Speed Control.

4. Monitor the output of the percent duty cycle from the Speed Control on the multimeter. Turn the potentiometer from the low setting to the high setting.

   Note: The throttle position on the ET will NOT match the percent duty cycle on the multimeter.

Expected Result:

The Duty Cycle should be between 4 and 10 percent at the low setting and between 90 and 95 percent at the high setting.

Results:

• OK - The Speed Control is supplying the correct signal. Proceed to test step 8.

• Not OK - The Duty Cycle is not correct on the multimeter. Proceed to test step D.

Test Step 7. Check the Droop Signal.

1. Remove the wire from the D terminal of the Speed Control.

2. Set the multimeter to "VDC". Press the "Hz" button twice so that the % symbol is displayed.

3. Place one probe of the multimeter on the D terminal of the Speed Control. Place the other probe on the -Battery terminal of the Speed Control.

4. Monitor the output of the percent duty cycle from the Speed Control on the multimeter. Turn the Droop Adjust Potentiometer from the low setting to the high setting.

   Note: The droop on the ET will NOT match the percent duty cycle on the multimeter.

Expected Result:

The duty cycle is between 15 and 85 percent. This range should be attainable.

Results:

• OK - The Speed Control is providing the correct Droop Signal. Proceed to test step 9.

• Not OK - The problem appears to be in the Speed Control.

  Repair: Temporarily install another Speed Control. Verify that the problem is no longer present. Reinstall the old Speed Control. If the problem returns replace the Speed Control.

  Stop.

Test Step 8. Check ECM Input.

1. Turn the ECS to the STOP position.

2. Set the multimeter to "VDC". Press the "Hz" button twice so that the % symbol is displayed.

3. Measure the voltage between ECM connector P2-24 and ECM connector P1-29.

4. Monitor the output of the percent duty cycle from the Speed Control on the multimeter. Monitor the percent Throttle Position on the ET. Turn the Speed Adjust Potentiometer from the low setting to the high setting.

Expected Result:

The Duty Cycle should be between 4 and 10 percent at the low setting and between 90 and 95 percent at the high setting. The percent Throttle Position should be between 0 and 100 percent for the above settings of the Speed Adjust Potentiometer.

Results:

• OK - The Duty Cycle is correct. Proceed to test step 5.

• Duty Cycle Not OK - The Duty Cycle is not correct.

  Repair: There is a problem in the wiring between P2-24 and the S terminal of the Speed Control. Verify that the low idle switch is functioning properly.

  Stop.

• Throttle Position Not OK - The Duty Cycle is correct but the Throttle Position is not correct. The ECM is not processing the correct signal.

  Repair: Replace the ECM. Refer to Troubleshooting, "Replacing the ECM".

  Stop.

Test Step 9. Check ECM Input.

1. Turn the ECS to the STOP position.

2. Measure the voltage between ECM connector P1-13 and ECM connector P1-29.

3. Set the multimeter to "VDC". Press the "Hz" button twice so that the % symbol is displayed.

4. Monitor the output of the percent duty cycle from the Speed Control on the multimeter. Monitor the Droop on the ET. Turn the Droop Adjust Potentiometer from the low setting to the high setting.

   Note: Do not overturn the Droop Adjust Potentiometer in the clockwise direction. The signal will become erratic.

Expected Result:

The Duty Cycle should be between 1 and 15 percent at the clockwise setting and between 85 and 99 percent at the counterclockwise setting. The Droop should be between 0 and 100 percent for the above settings of the Droop Adjust Potentiometer.

Results:

• OK - The Duty Cycle is correct. Stop.

• Duty Cycle Not OK - The Duty Cycle is not correct.

  Repair: There is a problem in the wiring between P2-24 and the S terminal of the Speed Control. Verify that the low idle switch is functioning properly.

  Stop.

• Droop Not OK - The Duty Cycle is correct but the Droop is not correct. The ECM is not processing the correct signal.

  Repair: Replace the ECM. Refer to Troubleshooting, "Replacing the ECM".

  Stop.