AUTOOL LM120+ Digital Manifold Gauge

1. Product Overview

The AUTOOL LM120+ Digital Manifold Gauge is a professional instrument designed for comprehensive testing and maintenance of HVAC and refrigeration systems. It provides accurate digital readings for pressure, temperature, and vacuum, facilitating efficient diagnosis and servicing of air conditioners and refrigerators. This kit includes the main gauge unit, temperature probes, and connecting hoses, offering a complete solution for refrigerant management.

Figure 1: AUTOOL LM120+ Digital Manifold Gauge and included accessories.

2. Safety Information

Please read and understand all safety warnings and instructions before operating the AUTOOL LM120+ Digital Manifold Gauge. Failure to follow these instructions may result in equipment damage, personal injury, or property damage.

• Always wear appropriate personal protective equipment (PPE), including safety glasses and gloves, when working with refrigerants.
• Ensure proper ventilation in the work area to prevent accumulation of refrigerant gases.
• Do not expose the device to extreme temperatures, direct sunlight, or moisture.
• Handle refrigerant hoses and connections with care to prevent leaks and refrigerant burns.
• Do not attempt to repair or modify the device. Refer all servicing to qualified personnel.
• Verify that the selected refrigerant type on the gauge matches the refrigerant in the system being tested.
• Keep the device away from children and unauthorized persons.

3. Package Contents

Upon opening the package, please verify that all items listed below are present and in good condition:

• 1 x AUTOOL LM120+ Digital Manifold Gauge
• 2 x Temperature Clamp Probes
• 3 x Refrigerant Hoses (Red, Blue, Yellow)
• 1 x User Manual (this document)
• 1 x Storage Case (if included with specific model variant)

4. Product Features

The AUTOOL LM120+ offers a range of advanced features for precise HVAC system analysis:

• Evaporation Pressure & Temperature Test: Measures the maximum pressure when refrigerant changes from liquid to gas and the lowest temperature during this phase. This helps assess the efficiency of the cooling cycle.
  

  Figure 2: Evaporation Pressure and Temperature Test display.

• Condensing Pressure & Temperature Test: Determines the minimum pressure when refrigerant changes from gas to liquid and the maximum temperature during this phase. Lower values indicate higher cooling cycle efficiency.
  

  Figure 3: Condensing Pressure and Temperature Test display.

• High / Low Pressure Temperature Test: Measures the temperature of the refrigerant within the high-pressure and low-pressure pipelines of the air conditioning system.
  

  Figure 4: High/Low Pressure Temperature Test display.
• Pressure Leakage Test: Calculates the pressure difference between an initial and a second test pressure to identify potential refrigerant leaks in the system.
  

  Figure 5: Pressure Leakage Test display.

• Refrigerant Type Setting & Observation Window: Allows selection of the appropriate refrigerant type for accurate measurements and provides a viewable window to observe the refrigerant filling status.
  

  Figure 6: Refrigerant Type Setting and Observation Window.

• Smart Digital Display: Provides clear and intelligent digital display of test results for pressure and temperature, reducing diagnostic time.
  

  Figure 7: Smart Digital Display.

5. Device Layout and Controls

Familiarize yourself with the components and controls of the LM120+ Digital Manifold Gauge:

Figure 8: LM120+ Digital Manifold Gauge Components.

6. Setup

1. Battery Installation: Open the battery compartment on the back of the unit and insert the required batteries (typically AA or AAA, refer to device markings if present). Ensure correct polarity.
2. Power On: Press the Power Button (11) to turn on the device. The LCD display (3) should illuminate.
3. Unit Selection: Press the Unit Button (9) to cycle through available pressure units (e.g., kPa, psi, bar) and the °C/°F Button (10) for temperature units. Select your preferred units.
4. Zero Calibration: Before connecting to a system, ensure all valves (13, 14) are closed and the hoses are disconnected. Press the Zero Button (6) to calibrate the pressure sensors to zero. This ensures accurate readings.
5. Connect Temperature Probes: Plug the temperature clamp probes into the Clamp-on Temperature Probe Sockets (2) on the top of the unit. Attach the clamps securely to the high and low-pressure lines of the HVAC system.
   

   Figure 9: Connecting temperature probes and hoses.

6. Connect Hoses:
   • Connect the blue hose to the Low Pressure Inlet (15) on the gauge and to the low-pressure service port of the HVAC system.
   • Connect the red hose to the High Pressure Inlet (17) on the gauge and to the high-pressure service port of the HVAC system.
   • Connect the yellow (or central) hose to the Refrigerant Inlet / Vacuum Pump Inlet (18) on the gauge. This hose will be used for vacuuming, charging, or connecting to a recovery unit.
   

   Figure 10: Detailed view of hose connection points.

7. Operating Instructions

This section outlines common operational procedures for the LM120+.

7.1. Selecting Refrigerant Type

1. With the device powered on, press the R+/R- Buttons (7) to scroll through the available refrigerant types (e.g., R134a, R22, R410a).
2. Select the refrigerant type that matches the system you are working on. This is crucial for accurate pressure-temperature conversions.

7.2. Performing Pressure and Temperature Tests

1. Ensure hoses and temperature probes are correctly connected to the system.
2. Slowly open the high-pressure (red) and low-pressure (blue) valves on the manifold to allow refrigerant to flow into the gauge.
3. The LCD display will show real-time pressure readings for both high and low sides, along with corresponding saturation temperatures based on the selected refrigerant.
4. The temperature probes will display the actual line temperatures (T1 and T2).
5. Compare the saturation temperatures with the actual line temperatures to determine superheat and subcooling, which are critical for system diagnosis.

7.3. Performing a Pressure Leakage Test

1. Connect the gauge to the system and pressurize it to the desired test pressure (ensure system can handle the pressure).
2. Close all manifold valves.
3. Press the Function Button (4) to navigate to the leakage test mode.
4. Press the Run/Stop Button (5) to start the leakage test timer. The gauge will record the initial pressure.
5. Allow the test to run for a specified period (e.g., 15-30 minutes, or as per system manufacturer's recommendations).
6. The display will show the elapsed time and the pressure difference. A significant drop in pressure indicates a leak.
7. Press Run/Stop Button (5) again to stop the test.

7.4. Refrigerant Charging/Evacuation

The LM120+ can be used in conjunction with a vacuum pump and refrigerant tank for system evacuation and charging. Always refer to the specific HVAC system's service manual for proper procedures and refrigerant amounts.

1. Evacuation: Connect the yellow hose to a vacuum pump. Open the manifold valves and the vacuum pump valve to evacuate the system to the desired vacuum level. Monitor the vacuum reading on the gauge.
2. Charging: After evacuation, close the manifold valves and disconnect the vacuum pump. Connect the yellow hose to a refrigerant tank. Purge the yellow hose of air. Slowly open the appropriate manifold valve (low side for vapor charge, high side for liquid charge with caution) to allow refrigerant into the system. Monitor pressure and temperature readings.

8. Maintenance

• Cleaning: Wipe the device and hoses with a soft, damp cloth. Do not use abrasive cleaners or solvents. Ensure no moisture enters the electrical components.
• Storage: Store the LM120+ in its original case or a protective container in a cool, dry place, away from direct sunlight and extreme temperatures.
• Battery Replacement: If the display becomes dim or the device does not power on, replace the batteries. Ensure the device is off before replacing batteries.
• Hose and Seal Inspection: Regularly inspect hoses for cracks, wear, or damage. Check O-rings and seals on connections for integrity to prevent leaks. Replace worn components as needed.

9. Troubleshooting

10. Specifications

11. Warranty and Support

For warranty information, technical support, or service inquiries regarding your AUTOOL LM120+ Digital Manifold Gauge, please contact AUTOOL customer service directly. Refer to the product packaging or the official AUTOOL website for the most current contact details.

Please have your product model number (LM 120) and purchase information ready when contacting support.