Press the "On" button at the top of the LS790B control panel. Press the "Alarm select" key that is located just above the "Off" switch toward the bottom of the control panel once if you want to activate the visual alarm indicator for leaks or twice if you want to activate both the visual and audible alarms. Do not press the "Alarm select" key if you only want to use the audible alarm.
Plug the provided earphone into your LS790B's earphone jack if you will be using the leak detector in a noisy area.
Depress the "Sensitivity" button just below the headphone jack until the LED indicator at the bottom of the unit is lit at the fifth position from the left.
Run the tip of the probe along any part of the refrigerator or air conditioner where you suspect there may be a leak. Listen for the alarm or watch for the LED panel to light up when the probe detects a leak.
Adjust the sensitivity upward by pressing the "Sensitivity" button once for each increment if you cannot detect any leaks but you are sure that there is loss of refrigerant from your appliance or system. Lower the sensitivity by pressing the button until an LED closer to the left of the panel lights up if the alarm constantly sounds or the entire LED panel remains lit.
Move the sensor back and forth three times over the suspected leak. If the alarm sounds all three times, then you have clearly identified the source of the leaking refrigerant. If not, continue checking other parts of the equipment.
Press the "Lock out" button and listen for a dual alarm as you move the probe to pinpoint the exact source of a leak if the alarm sounds over a wide area of the equipment you are testing. The specific point at which you placed the probe when the dual alarm sounded is the exact source of the leak.
Clear the memory by pressing the "Reset" button (this may be marked "Clear") next to the "Sensitivity" button and press the "Lock out" button again if you are unsure of the exact point where the dual alarm sounded.
Press the "Reset" button to clear the memory and reset the unit. Test for any further leaks. Press the "Off" key at the bottom of the control panel to turn the unit off.
- Shield any outdoor search areas from the wind with aluminum foil, as the detector does not work in windy conditions. Leak test an automotive air conditioner evaporator core by turning the air conditioner blower to its highest setting for 15 seconds. Turn the blower off and wait 10 minutes before you insert the probe into the blower resistor block or the closest dry opening to the evaporator in the cooling system's case.