If in such a case, check the output continuity of the relay (as shown).

• If there is no continuity, replace the relay with a new, identical one.
• If the relay is conducting normally, measure the output voltage of the laser power supply (as shown).

• If the output voltage reads 0, replace the laser power supply with a new, identical one.
• If the output voltage reads a normal 12V, measure the voltage at the supply plugs for the air pump and exhaust fan (as shown).

• If the supply plug voltage reads 12V, replace the air pump and exhaust fan with new, identical ones.
• If the voltage of the power supply plug reads 0, set the multimeter’s beeper on.

Check the continuity between the 12V port of the laser power output and the relay output.

• If the line is conductive, continue to check the continuity between the laser power output and the 12V terminal of the air pump/exhaust fan power supply.
• If the 12V ports prove normal, check the continuity between the laser power output GND and the air pump power supply plug GND; fix any disconnected point.