Testing the Natural Gas Detection System Sensor

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Daimler Truck strongly recommends that all operators follow California Code of Regulations (CCR) inspection requirements, regardless of where the vehicle is operated. According to Title 13 CCR Section 935 (2), gas detection systems should be tested three times per year at equal intervals. The testing procedure should simulate the same operating environment in which the vehicle is used. Test results validating the performance of the gas detection system within the parameters established by the component manufacturer and NFPA 52 should be maintained as a permanent part of the vehicle service records. Use of alcohol, propane, and other harsh liquids or gases are not acceptable methods of testing.

Test the sensors three times per year, after any system component has been replaced, or if the vehicle was involved in an accident or fire. The gas detection system sensors must be tested regularly by a trained technician using certified test equipment that satisfies CCR Section 935 (2) or NFPA 52 regulations (Xintex Methane testing kit model: MTK-20-50 or similar).

Daimler Truck recommends the highest level of safety validation if there are multiple validation requirements in the state or locally where the vehicle is operated or parked.

    Note: Use only approved test gas cylinders for conducting sensor validation. Although the methane concentration of these cylinders is not at a flammable level, proper safety procedures must be maintained, as with any compressed gas cylinder. Make sure that the shut-off valves are fully closed when not in use.

    When the system is functioning normally, the control panel should display a green System Normal LED that is turned on, with no system faults.

  1. Energize the methane detection system by supplying low-voltage (LV) power to the cab, and allow the system to warm up for one minute. See Fig. and Fig. .

    Fig. 1, Alarm Panel Configuration

    Fig. 2, System Normal

  2. Press and hold the Test button for one minute. The system will perform a self-diagnostic test, which will include the illumination of the Trace Gas and Significant Gas Concentration lights, as well as the sensor Fault lights. See Fig. .

    Fig. 3, Expected Reaction to Depressed Test Button

  3. To test for sensor detection, disconnect the sensor harness and observe the control panel for the following changes:

    • Green: System Normal LED turns off.

    • Amber: System Fault LED turns on.

    • System Reset LED turns on.

    • Amber: Sensor Zone LED begins flashing, indicating the sensor zone that does not have a sensor connected (e.g., Sensor Zone 1 = one flash, Sensor Zone 2 = two flashes, etc.).

    If these indications do not occur within 30 seconds, the system is faulty and must be replaced. See Fig. .

    Fig. 4, Expected Reaction to Missing Sensor

  4. Reconnect the sensor harness. The control panel should return to the System Normal state.
    5. Note: Do not test with 20% LEL gas for more than 30 seconds.
  5. Connect the regulator, hose, and adapter to the 20% LEL gas cylinder securely.
  6. To test for trace gas detection, open the gas regulator and place the adapter over the sensor, ensuring the sensor is completely covered; observe and record any condition changes on the control panel. See Fig. and .

    • Green: System Normal LED turns off.

    • Amber: Trace Gas LED begins flashing.

    • System Reset LED turns on.

    • Amber: Sensor Zone LED flashes to indicate the sensor zone that is detecting gas.

    If these indications do not occur within 30 seconds, the sensor is faulty and must be replaced.

    Fig. 5, Fully Covered Gas Sensor

    Fig. 6, Expected Reaction to Trace Gas Detected

  7. Remove the test gas and allow the sensor to air out. Once the gas has cleared, the control panel should return to the System Normal state, which may take up to 30 seconds.
  8. Connect the regulator, hose, and adapter to the 50% LEL gas cylinder.
  9. To test for significant gas detection, open the regulator and place the adapter on the sensor. Observe and record any condition changes on the control panel. See Fig. .

    • Green: System Normal LED turns off.

    • Amber: Trace Gas LED begins flashing.

    • Red: Significant LED turns on.

    • System Reset LED turns on.

    • Alarm begins sounding.

    • Amber: Sensor Zone LED flashes to indicate the sensor zone detecting gas.

    If this sequence does not occur within 60 seconds, the sensor is faulty and must be replaced.

    Fig. 7, Expected Reaction When Latching

  10. Remove the test gas and allow the sensor to air out. Once the gas has cleared, the control panel should return to the System Normal state, which may take up to 60 seconds.
  11. To test for latching functionality, open the regulator and place the adapter on the sensor. Observe and record any condition changes on the control panel.

    • Green: System Normal LED turns off.

    • Amber: Trace Gas LED begins flashing.

    • Red: Significant LED turns on.

    • System Reset LED turns on.

    • Alarm begins sounding.

    • Amber: Sensor Zone LED flashes to indicate the sensor zone detecting gas.

    If this sequence does not occur within 60 seconds, the sensor is faulty and must be replaced.

    12. Note: For testing purposes, the silence switch was used.
  12. Once significant gas has been detected, keep the adapter on the sensor for an additional 60 seconds to activate the control panel’s latching functionality. Observe and record the condition changes after one minute. See Fig. and Fig. .

    • The top red LED turns on.

    If this does not occur within 60 seconds, the system is faulty and must be replaced.

    Fig. 8, Expected Reaction When Latching

    Fig. 9, Latched Configuration After Gas Has Cleared

  13. Once the gas has cleared, the control panel will remain in the latched state. To return to the System Normal state, press the Reset button.
  14. Repeat steps 3 through 13 for all sensor zones. Replace any sensors that fail their tests.
Note:
Parent topic: Electrical, Instruments, and Controls
Document Number: 0000121172
Manual Publication Date: 2025-02-11
Topic Publication Date: 2026-11-09