Sat Jul 17 2021

LOW COOLANT message on startup

Hello! we have a used 2002 gentlelase plus. The first time we added distilled water to the reservoir and it functioned normally, we were able to do a calibration of the handpiece and fired off a few test shots at 10 J. We turned it off then back on a few minutes later and it started displaying "low coolant" and starts counting seconds and minutes. (we turn it off immediately of course.) upon investigation, we found glass fragments in the water reservoir (most likely from a blown out flashlamp. we will be taking it apart to replace the lamp if so) The level of distilled water added is correct. We even drained the water and added new water and it still displays the same message. Therefore, someone suggested that the "low coolant" message might mean the system is not cooling the distilled water hence the water got too hot and the flashlamp may have blown as a result. so we do not want to replace the lamp and then have it blow out also before resolving the "low coolant" issue. we did notice that the big fan on what looks like a radiator that the water passes through to probably cool it, does not turn on when the system is turned on. (so is the radiator fan supposed to turn on as soon as the system turns on?) however we tested the fan separately out of the system and it does work when supplied with 24 V. if ANYONE has any insight on the "low coolant" message issue please let us know! it may also be possible that a board component or relay or something went bad and is not turning on the cooling system?? or is "low coolant" a problem with the the water level sensor inside the reservoir tank?? ANY input would be helpful! Thank you so much! Jessica :)

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Mon Jul 19 2021Reply from Erik J
avatar placemark

The error is not related to temperature.  Low Coolant means that the level is low.  Since you are adding water and the error persists, the problem is likely due to a failed level sensor.  

The level sensor is located inside the water reservoir and they are known to fail rather often.  

Let me know if I can be of further assistance. 


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Tue Jul 20 2021Reply from Erik J
avatar placemark

We had a big internet outage here. I guess that's why my reply posted a bunch of times. 


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Sat Jul 24 2021Reply from jakem
avatar placemark

Thank you Erik. You are absolutely correct. After reading your message what we did was bypass the fluid level sensor by unhooking it and closing the circuit with a wire to basically trick the system into thinking the fluid sensor is floating normally and that resolved the low coolant message and the system went directly into warming up. This confirms the problem is a bad fluid sensor.

i want to ask your assistance further in the next issue:

as we mentioned before, the first time we turned on the system it worked normally and calibrated fine and we fired a couple shots at 10 J.
the second time we got a FAULT 5 (which is a calibration error) followed by the low coolant error.

when we removed the fluid sensor from the reservoir we noticed pieces of glass and broken metal O rings. After bypassing the low collant issue the laser would not calibrate and would display fault 5.

we took the head apart thinking it would be a broken flashlamp since those were old also and came with the used unit. The flashlamps were not broken but there was glass in the head around them from broken flow tubes and broken rings from the light blocking rings on either side of the flow tubes.

we ordered a new set of flow tubes and light blocking O rings to replace the broken ones and decided to inspect the Alex rod.

Surprisingly, the rod had inner shear and what looks like internal cracks in around half of its length. the surface is smooth. (i want to attach a photo of the rod but i can't figure out how to do it here). So now we are thinking the rod is bad or can the calibration error be from the broken flow tubes and glass that was around the flashlamps inside. Does the rod get these internal cracks with time and still function?

is there a chance after installing the new flow tubes and light blocking kit, the rod would still have life in it?

thank you again for your assistance and expertise!


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Sun Jul 25 2021Reply from Erik J
avatar placemark

There should be no appearance of anything resembling cracks when looking through the rod longitudinally or end-to-end. Water flow problems will most-certainly damage the rod..  

If the rod is cracked, you will need to replace it.  Those start at about $10,000.  Sorry to bring you bad news.  You can probably by a whole laser for less than that - if you can find one with a good rod.  

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Mon Jul 26 2021Reply from jakem
avatar placemark

I found someone selling a full head with the rod and flashlamps in excellent working order for 3000$ and went ahead and purchased it. It has a 30 days return warranty on it also which is good.

Now the big question is why did this happen in the first place and how to ensure it does not happen to the new head and rod!?

Again the first time we received the old one, it has not been turned on for years. We filled it with water, turned it on and calibrated and fired off 2 shots normally. The second time we turned it on (20 mintues later) it had the loud noise in the pump from the broken O rings and glass that slipped into the pump. So it would appear that the tubes, o rings and rod shattered altogether on that first time we turned it on and fired the 2 shots.

any theories or suggestions so the same doesn't happen with the new head?

When we opened the head, the rod was cracked in the fashion mentioned, one of the flow tubes cracked to pieces, 2 of the o rings and a small metal part from the light blocking kit inside the head were broken into pieces. the quartz supposedly white triple bore was yellow to brown in color especially at both ends.


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