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Laser Not Firing: Interlock Testing

Use this guide when the machine runs a job, but the laser does not fire or the milliamp meter does not move during a pulse.
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How to Test the Interlock System on Your Boss Laser

If your Boss Laser is running a job but the laser is not firing, or the milliamp meter is not moving when you try to pulse the laser, one possible cause is an interlock issue.

The interlock system is designed to prevent the laser from firing unless certain safety conditions are met. This guide walks you through the basic testing process for the main interlock points on your machine.

Common Symptoms of an Interlock Issue

You may need to test the interlock system if:

  • The laser head moves, but the laser does not fire.

  • The machine runs the job, but nothing is marked, engraved, or cut into the material.

  • The milliamp meter does not move when pulsing the laser.

  • The laser fires from the power supply test button but not from the control panel.

Important Safety Notes

Laser power supplies contain high-voltage components. Use caution when working near the power supply or electrical connections.

Before disconnecting or reconnecting plugs, turn the machine off.

Do not operate the machine with interlocks bypassed except for temporary diagnostic testing. Interlocks are part of the machine’s safety system and should be restored before normal operation.

If you are unsure about any step, contact Boss Laser Tech Support before continuing.

Tools Needed

You will need the following tools:

  • Multimeter with continuity setting

  • Six-pin bypass connector

  • Chiller bypass connector

  • Small bypass pin, which can be made from a paperclip

  • Magnet for testing the door interlock

  • Allen wrench for adjusting the door interlock, if needed

The six-pin bypass and chiller bypass are typically included in the machine toolbox. The multimeter and magnet are not usually included.

Step 1: Confirm Power to the Laser Power Supply

Before testing the interlocks, confirm that the laser power supply is receiving voltage.

The laser power supply is located in the right-side cabinet of the machine.

Set your multimeter to AC voltage.

For a 120V machine, set the meter to the 200V AC range.

For a 220V machine, set the meter to the 600V AC range.

Place the red probe on the red wire of the three-wire power connection. Place the black probe on the green/yellow ground wire.

If the correct voltage is present, the power supply is receiving power and you can continue to the next test.

If the power supply is not receiving voltage, stop and contact Boss Laser Tech Support.

Step 2: Test the Laser Power Supply and Laser Tube

This test helps confirm whether the power supply and laser tube can fire independently of the control panel and interlock system.

Turn the machine off.

Locate the six-pin connector on the laser power supply. Disconnect the existing six-pin plug and install the six-pin bypass connector.

Turn the machine back on.

Locate the test button on the laser power supply. It is usually positioned between the power supply connections.

Briefly press the test button.

Watch the milliamp meter and the material under the laser head.

If the laser pulses and the milliamp meter moves, the laser power supply and laser tube are likely working. Continue to the door interlock test.

If the laser does not pulse from the power supply test button, contact Boss Laser Tech Support.

Note for Gold Power Supplies

If your machine has a gold power supply, you may need to loop pins three and four using the cable on the six-pin connector. After looping those pins, try pulsing from the control panel.

Step 3: Test the Door Interlock

The door interlock prevents the laser from firing if the lid or door is not properly closed.

To test the door interlock, place a magnet directly on top of the door interlock sensor. This should manually trigger the interlock.

With the magnet in place, press the Pulse button on the control panel.

If the laser fires, the interlock sensor is working, but the magnet on the lid may not be making proper contact with the sensor when the lid is closed.

In that case, adjust the door interlock sensor.

The interlock is held in place with two Allen screws. Loosen the screws slightly and angle the interlock outward so it is positioned closer to the magnet on the lid. The sensor should almost be peeking out.

After adjusting it, close the lid and pulse the laser again.

If the laser fires and the milliamp meter moves, the issue was likely an alignment problem between the lid magnet and the interlock sensor.

Step 4: Check Door Interlock Continuity

If the laser still does not fire with the magnet placed directly on the door interlock, check the interlock for continuity.

Set your multimeter to continuity mode. Touch the two probes together to confirm the meter beeps or shows continuity.

Locate the door interlock connection underneath the control panel and disconnect it.

Keep the magnet on top of the door interlock sensor.

Place the multimeter probes on the male side of the connector.

If you have continuity, the door interlock is working.

If you do not have continuity, use your small bypass pin to temporarily bypass the door interlock by inserting it into the female side of the connector.

With the bypass pin installed, try pulsing the laser from the control panel.

If the laser still does not fire, leave the temporary bypass in place and continue to the water flow sensor test.

Step 5: Test the Water Flow Sensor

The water flow sensor confirms that cooling water is moving through the laser tube. If the sensor does not detect flow, the laser will not fire.

Make sure your chiller is turned on before testing the water flow sensor.

Locate the water flow sensor quick-disconnect plug. Disconnect it.

Because water should be flowing through the system, the float inside the sensor should be triggered.

Use your multimeter in continuity mode to test the sensor connection.

If the water flow sensor has continuity, plug it back in and continue to the chiller signal test.

If the water flow sensor does not have continuity, insert the bypass pin into the female side of the connector, similar to the door interlock bypass test. Then continue to the chiller signal test.

Step 6: Test the Chiller Signal

The chiller signal is another part of the interlock system. This signal confirms that the chiller is active.

Make sure the water chiller is on.

Turn the laser machine off before checking continuity.

Go to the back of the machine where the chiller signal cable connects. On the back of the plug, there should be two wires.

Place one multimeter probe on each wire and check for continuity.

If you have continuity, install the chiller bypass connector and try pulsing the laser from the control panel.

If the laser fires with the chiller bypass installed, contact Boss Laser Tech Support for the next step.

If the laser still does not fire, leave the bypass in place and continue to the final power supply continuity check.

Step 7: Check Continuity at the Power Supply

For the final test, check continuity at pins three and four on the six-pin power supply connector.

Set your multimeter to continuity mode.

Place one probe on pin three and the other probe on pin four.

Make sure all interlocks are active:

  • The chiller should be on.

  • The door should be closed.

  • Any tested interlocks should either be connected normally or temporarily bypassed for testing.

If you have continuity between pins three and four, the interlock circuit is complete.

If you do not have continuity, contact Boss Laser Tech Support.

What to Do After Testing

Once testing is complete, remove any temporary bypass pins or bypass connectors unless Boss Laser Tech Support instructs you otherwise.

Reconnect all interlock plugs and restore the machine to its normal operating configuration.

Do not continue using the machine with interlocks bypassed.

Contact Boss Laser Tech Support

If the laser still does not fire after completing these tests, or if you are unsure about any result, contact Boss Laser Tech Support.

Email: techsupport@bosslaser.com
Phone: 407-878-0880

LS Series Resources

Start with the LS manual, quick start, and first diagnostic checks.

The LS Series page should help owners quickly confirm they are in the correct support area, then route them to common fixes or their exact model page.

In event that your laser does not fire you will have to conduct interlock testing, this will allow for Technical Support to determine what interlocks are causing the laser to not fire. If you need help at any time along the way, please reach out to us at techsupport@bosslaser.com or call 407-878-0880

DOWNLOAD PDF HERE: 👉 Interlock Testing

Equipment and Tools needed:

  • Chiller bypass
  • 6-Pin bypass
  • Interlock bypass OR Paperclip
  • A multi-meter

Video Instructions

https://www.youtube.com/watch?v=kpE6KLLEgpE

Make Sure Power Supply Is Powering On

  • Locate your power supply unit, this is found through the right side of the machine through the large white door on the bottom.
  • The power supply is either going to be gold or black in color. It will have a six-pin green connector and a three-pin green connector going into it. On the other side it will have a larger red wire and black wire as well.
  • Take a look at the power supply with the machine powered on, do the lights work and are the fans on the power supply spinning?
    a. If yes, please move onto the testing below.
    b. If no, please check the three-pin connector along the side of the machine on three yellow wire with a green tracer and the red wire. This would be your hot lead and ground lead.
  • If you have 120V going into the power supply but it is not powering on, then the power supply is faulty and will need to be replaced.

⚠ Please reach out to us at techsupport@bosslaser.com or call 407-878-0880 for a replacement power supply.

Six Pin Bypass Test For 60W, 100W and 150W Machines

  1. Locate your 6-pin bypass.
  2. Make sure that your machine is powered off.
  3. Locate your mA meter, this will be above your laser keypad and temperature gauge.
  4. Locate your power supply (PSU). Normally will be on the right-hand side of your machine.
  5. Take out your 6-pin from the laser power supply.
  6. Replace this connector with the six-pin found in your tool box with the wire loop.
  7. Locate your test button on the power supply, it should be a red push button that says test or laser
  8. Power your machine back on.
  9. Use the test button while viewing the mA meter. If the laser fires then you have an interlock issue.
    • If the laser does not fire, then you will need to complete the RESISTOR TESTING document.
    • If the laser fires with the 6-pin bypass you may continue testing below.

Six Pin Bypass Test for A Gold PSU

  1. Locate your 6-pin bypass.
  2. Using the screwdriver provided in your tool box you will remove the looped wire from the six-pin connector that was found from the tool box.
  3. Make sure that your machine is powered off.
  4. Locate your mA meter, this will be above your laser keypad and temperature gauge.
  5. Locate your power supply (PSU). Normally will be on the right-hand side of your machine.
  6. Take out your 6-pin from the laser power supply and add the wire that you removed to pins 3 & 4 of your 6-pin connector. This will go on top of what is already there in addition.
  7. Plug the 6-pin connector back into the laser power supply.
  8. Power your machine back on.
  9. Go to the keypad of your laser machine, and make sure the power is set to 95%.
  10. Once power has been verified, hit the pulse button on the key pad. 11. If the laser does not fire then you will need to complete the RESISTOR TESTING procedure.
  11. If the laser fires or the mA meter moves then you have an interlock issue and you may continue testing below.

Testing the Door Sensor

We will be testing the door sensor. This is a safety switch that tells your laser not to fire with the door open. You will need a magnet to do the following test. Your regular 6-pin connector should be plugged in, not your 6-pin bypass.

  1. What you are going to do is place the magnet directly on top of the door contact. The door contact will be in the door jamb when you lift the hood of the machine up.
  2. With the magnet on top of the door contact you will go to the keypad and see if the laser will fire
  3. If the laser fires, then the door interlock is the issue, and this will need to be adjusted
  4. Since the laser fires with the magnet on the contact this indicates that it does not make good contact with the hood magnet.
  5. To fix this you are going to loosen the two Allen screws on the contact and raise the contact up as high as it can go (still at an angle) and the drop the hood down and see if the laser fires with the door closed.
  6. IF THE LASER DOES NOT FIRE WITH THE MAGNET ON THE DOOR CONTINUE TESTING TO THE CHILLER SIGNAL CABLE PORT LOCATED ON THE BACK OF THE MACHINE

Testing the Water Chiller Signal Cable

We will be testing the chiller signal cable port, this will be located at the very back of the machine, labeled as chiller signal.

  1. Locate the chiller signal cable, this will be found on the exterior of the machine labeled chiller signal
  2. If the cable from the chiller to the machine is in its place you will remove this wire from the connector
  3. With this connector removed you will go to your tool box and locate the chiller bypass plug
  4. Go to the back of the machine and install the chiller bypass plug
  5. With the bypass plug installed you will go to the keypad of the machine and see if the laser will fire
  6. If the laser does fire, then the cable going to the chiller has gone out and you will likely need a new one
  7. IF THE LASER DOES NOT FIRE THEN YOU WILL MOVE ON TO THE FINAL INTERLOCK TEST WHICH WOULD BE THE WATER FLOW SENSOR. YOU WILL LEAVE THE MAGNET ON THE DOOR AND THE CHILLER BYPASS IN THE SIGNAL CABLE PORT.

Testing the Water Flow Sensor

  1. Locate the water flow sensor, this can be found in-between the power supply and the frame of the machine, it will be a large white cylinder that will have the water in and out hoses attached.
  2. Once this has been located you will remove the male and female connector to disconnect the wiring of the water flow sensor.
  3. With the wiring disconnected you will take your paper clip and plug it into the female end of the connector, one end of the paper clip on one side and the other end on the other side.
  4. With the water flow sensor completely bypassed you will see if the laser machine will fire from the keypad.
  5. If the laser fires, then the water flow sensor is the culprit and will need to be replaced.
    a. Before we replace the water flow sensor we need to verify if it just slid out of position
    b. Please take the paper clip off and reconnect the male connector to the female connector as it was before
    c. Take a small screwdriver and loosen the screws on the plate that has the wires going to the connector
    d. Slide the plate to the middle or opposite end(s) of the screw groove and retighten the screws (you may need to repeat steps d – f up to 2 times)
    e. Turn the machine back on
    f. Press the Pulse or Laser button on your Control Panel
    g. If the laser fires, then you have fixed your issue and there’s no need to continue troubleshooting or replace the Water Flow Sensor as it was just out of position
    h. If the laser still doesn’t fire after moving the plate to all of the other possible positions on the groove, then the Water Flow Sensor must be replaced
  6. IF THE LASER DOES NOT FIRE THEN YOU WILL NEED TO CHECK FOR CONTINUITY USING A MULTIMETER.

Testing the Interlock Testing

If none of the interlock testing checks out, you will need to run continuity tests on all components until you find the culprit.

  • Turn your multimeter to check for continuity with an audible beep, to do this you can refer to the picture, this shows where the meters setting should be set for.
  • When you tap the red and black leads together while in this setting it will beep, confirming that the circuit is complete and has continuity on it.

Door Sensor Male End

  1. Turn the machine off
  2. Place a magnet on the door contact
  3. Unplug the door contact by tracing down the wire to the female/male connector
  4. Turn your meter on and set it for continuity
  5. Once you have this plug undone and the male end in your hands, you are going to put the meter leads on both silver prongs, one prong for red and one for black.
  6. With a magnet on the door contact you should have continuity, and once the magnet is gone, continuity will disappear along with the beeping.
    a. YES continuity: This means your door contact is good. You are losing continuity somewhere else; you will proceed with checking the water flow sensor.
    b. NO continuity: Door contact is bad; you will need to reach out to Tech Support

Testing the Water Chiller Signal

The last interlock switch, which is the water chiller signal cable. Its located on the back of your machine. Where your chiller plugs in. If you have a water pump you will already have this plugged in.

  1. Making sure all the other interlocks we have tested are plugged back in.
  2. Locate your chiller bypass.
  3. Plug the chiller bypass into the chiller signal port on the back of the machine
  4. Have machine off and the water/chiller on
  5. Put the multimeter on the inside of the chiller signal port where the wires attach, red on one black on the other, do you have continuity?
    a. Yes, bypass plug is good, laser should be able to fire, continue testing b. No, the issue is coming from either the bypass plug or the port itself, contact Technical Support.

Lastly, if all the interlocks have continuity on it and check out, you will be able to check the six-pin connector on the power supply, this is a matter of putting the leads on pin 3 and pin 4. Once you have the meter on pin 3 and 4 you will have continuity and a beep indicating that you are ready to fire your laser. If you still do not have continuity at this point, then please contact Technical Support.