Cooling Issues - System Will Not Work

System will not run. Stuck on perpetual cooling.

Yes… I’ve tried all your suggestions posted on the forum.

What model :glowforge: do you have?
What is the ambient temperature, measured, next to your :glowforge:?

Sounds like you’ve already seen the posts where we say:

Your Glowforge features a closed-loop liquid cooling system that uses the air from the room to remove heat. It is designed to be used when the temperature next to your Glowforge is between 60 degrees Fahrenheit (16 Celsius) and 75 degrees Fahrenheit (24 Celsius). To check, put a room thermometer next to the right hand side of the Glowforge; it draws in air from underneath, on the right.

You can try any of these things to improve warm-weather performance:

  • Try printing with no material on the bed (so as not to generate smoke and fumes) and no exhaust hose attached. If this works, then the problem may be that your exhaust hose is constricting the flow of air out of the unit, preventing cooling.

  • Examine the bottom-right side of your Glowforge, and ensure that there is no fabric or other flexible material underneath it, like a tablecloth. There are air intake vents, and if they become obstructed, it makes cooling less effective.

  • Try pointing a fan at the right side of your Glowforge. If there is warm air around the intake, this could help it cool off.

  • Power off your Glowforge when you are not using it. When your Glowforge sits idle, the fans are off, so heat can build up

  • Just wait. Your print may take a little longer when it’s warm, but your Glowforge will protect itself and make sure it cools enough to prevent any loss of power or damage. It’s clever enough to pick up from exactly where it left off, even if it needs to pause to cool down during the print!

  • Ensure that the sun isn’t shining on the lid. This could cause the inside of your Glowforge to heat up.

  • If you are venting outdoors, ensure that extreme temperatures or humidity do not enter the Glowforge unit through the exhaust hose. Disconnect the hose from the outside air when the Glowforge is not in use.

  • Turn your Glowforge off and open the lid for a few minutes before trying again. It’s possible for the air in your Glowforge to heat up, just like a car in the sun on a hot day, opening the lid will help that warm air to escape and your Glowforge to cool down.

If that’s correct, the next steps are to let us know the following so that we can investigate further:

  1. A description of the things you tried and what happened

  2. If possible, place a thermometer next to your Glowforge on the right hand side and measure the temperature there; if not, estimate the room temperature

  3. The date and time (including time zone) when you had the problem

  4. Take a picture of the exhaust hose behind your Glowforge that includes the part where it connects to your Glowforge, and the part where it exits the room

  1. Tried cutting nine (9) 1/8" thick acrylic letters - did not work, went directly to cooling. Machine was off prior to attempt.

  2. It’s unreal that you have to ask me to use a thermometer to operate your laser system - but ok… yea, temp. is around 71

  3. 9/18/2018 from 1-4pm

  4. Exhaust hose travels no more than 3 feet

20180918_161756 20180918_161700

I’m not sure how time travel works, but I’d imagine there’s some heat generated at some point. That could be affecting the ambient temperature in the room.

Please tell us that the exhaust hose is not left open like that on the outside. Has a vent cap? My GF wouldn’t last a single night without a black snake or chipmunk making a home inside that hose.

BTW: Depending on how the house breaths and with a short hose open to the outside, the outside temperature may be the inside temperature of the unit.


nope… it’s attached to an air filter - had to detach to test heating issues

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So temp is measured 71F or you’re guessing?
If you have a Basic and it’s really ~75F, that’s the high end of the stated specification for operating temperature.
You would be surprised that people try to operate their Glowforge outside it’s stated operating parameters, that’s why you have been asked to measure the ambient temperature.

Since you had a 3rd party air-filter previously attached, have you cleaned the Glowforge to ensure that there was not any buildup of dirt due to backpressure as a result of an airfilter?


And it’s really the temp inside the GF that matters - it’s often a couple/few degrees warmer inside due to the heat generated by all the components. If that’s over the stated operating temperature it might never cool down.

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How much does the air filter block the full exhaust flow? I am thinking that if there is back pressure from the filter in the air flow, dust and debris isn’t the least of the problem, but a compromised airflow might cause a temp issue.

Does your place use a whole house fan or swamp cooler?

If you house is in a negative pressure environment (drawing air from outside), then you have heat being drawn into your Glowforge :glowforge: and warming it up above operating temperature.

And yes, I discovered that my whole house fan was doing just that.


I extracted the logs from your Glowforge from the time you mentioned. The logs indicated that the coolant in your Glowforge was 91.5F.

There are a number of things that can cause the coolant in your Glowforge to be too warm to start a print. For example, similar to a car left in the sun, the glass lid can create a green-house-effect trapping the heat from the sun. Leaving the lid open when not printing helps.

When you receive a message that your Glowforge needs to cool, if the air the Glowforge is drawing in through the intake fans (at the front right corner) is cooler than the temperature of the coolant, your Glowforge will cool down towards the temperature of the air in the room. If the room temperature is in the operating temperature range, you Glowforge should be able to cool enough to be able to begin printing again.

There are two things you can do when you see the cooling message and your room is at the correct temperature:

  1. make sure that there isn’t anything obstructing airflow,

  2. allow your Glowforge to cool

Note: If you cancel prints it will turn off the cooling fans and any heat stored within the coolant won’t be able to dissipate as quickly.


This is 100% wrong AND inaccurate.

There’s NO WAY this coolant is at 91.5 – impossible inside a room temp controlled environment.

When you operate the glowforge it generates at lot of heat. The inside of the glass laser tube gets HOT. There is cooling liquid which is circulated through the tube to cool it down. It is this cooling liquid temperature that they pulled from your records as being 91.5 degrees. The air in the room is what is used to cool the cooling liquid down (unless you have a pro model then it has an extra cooling system). If the temperature in the room is above 75 degrees for a basic unit GF is basically telling us that it can’t cool down the cooling liquid enough to operate the GF. They don’t tell us at what temperature the coolant liquid triggers the “cooling” error and we don’t have any way to monitor it. It is completely possible that your cooling liquid temp was 91.5 degrees.


I thought that was the issue too, so I removed the filter. Nothing changed.

This became an issue shortly after they updated their software - I’m confident it’s the code conflicting with hardware (heat sensors) or the sensor is not working.

if that were the case, we would probably see a raft of posts on this issue.


Agreed, if it were a simple code problem, we’d see more people reporting it.
It’s more likely an isolated Hardware sensor issue, or related to using an unsupported air filter causing debris buildup somewhere.


Could be the thermistor but they usually don’t die this way.
If it is software we’d see a rash of the same problem.

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How did you measure the temperature to verify the inaccuracy?


Three foot, straight exhaust run… What was your high temperature the other day - 9/18?

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