Klarus G20 - help needed

My Klarus G20 does not light anymore.

The indicator light in the side switch works normally…full batt, lock-out mode (in and out of it), blinks as it should.

The rear and side switch has crisp click when activated.

Tube is clean and makes contact with the driver I guess.

Any suggestion on what trouble-shooting tips to try would be greatly appreciated.



Check if the LED removed itself from the PCB? Happened to me once but that is the fault of my shitty reflow. It seemed to be still attached slightly but I tried to prod the LED with a tweezer and it was loose. Might worth checking.

Looking at the led front from the lens, it looks as well-placed as it was new….the driver on the other side is still tight, I held the spring on the + plus side and it is tight, no rattle or any small movement.

Does it use a protected cell, the 2 links did not mention this?

What voltage does the cell read with a voltmeter?

Could you test if it will discharge thru an external load? Maybe charge it with an external charger.

The oem 26650 is fully-charged, both from the lighted Green switch indicator AND as tested by my multi-meter outside the light.

On further searching, it is a protected cell with circuit board at the cathode end. A fault in the bms would likely disable the FET in the discharge path; that’s why an external load test would be needed to rule that in/out. Just reading the OCV of a protected cell doesn’t prove that it is functional or “good”.

Since the oem 26650 gives a reading 4.15v, is there some other way to further test it?

I tried a Shockli 26650 in the tube and charged it, and my USB meter gave out a reading of .4A charging rate.

Did the light work with the other cell?

If the cell protection has activated, then the cell will not drive current thru a load.

If the cell will deliver 1 or 2 or 5 Amps during a load test, then the cell is likely OK and the problem is in the flashlight.

To load test a cell, you will need some wire and a low resistance device to draw current, e.g. a 20W 2 Ohms resistor would draw about 2 Amps, or you might connect an old car headlight (12V, 50W) or bulb across the cell as a load. Note that this will create some heat so watch out for your fingers when touching the load.

Read about cell testing from an expert here:

Use your voltmeter to monitor the cell voltage while it is loaded to watch it during discharge and stop the test if the cell voltage goes too low. If you meter will measure current, then you could monitor that also to get a reading for the load.

Neither the light worked with the Shockli cell.

I might try the oem, protected Klarus 26650 cell with my other 26650 light and see if it will work, for as previously suspected, it might display voltage but just not enough amps to power the indicator switch lights but not the main led.

Edit: I just tested the oem Klarus 26650 cell in my Nightwatch IRAlight, my first white-flat Osram light. ( Shoot-out: Mateminco MT35mini (FT03), Mateminco TO2 (FT02) and the small Nightwatch NI01L IRAlite Osram White Flat )

The cell powered the IRAlight just fine.

Could you try doing a continuity test with a DMM on the + and - pads of the LED PCB? See if that lights up the LED since the battery does not seem to be the issue.

I removed the bezel and lens/reflector… then performed a continuity test on the Red and Black wires soldered on the LED pcb, and there is no continuity.

Busted LED?

Swapping the battery to another light was a good check to prove the cell is not locked up by the protection.

Unfortunately it’s pointing back to some issue in the flashlight, like a blown FET in the output driver section.

Looks like the driver can be accessed out the front after removing the bezel and reflector,

Does it mean a lack of continuity does not mean a busted LED but possibly of blown FET?

Pardon my naivete, just some very basic knowledge here bro.

Sorry got the tests mixed up. Use the diode test rather than the continuity. The icon should look like this

If it doesn’t light up it might be worth reflowing first before going through the headache of diagnosing the driver.

Oh, my electrical trouble-shooting adventure just ended with your post about the diode thing…time to look for some friends who are knowledgeable about this.

Any other possible cause of the problem?

I don’t know if the “power tube” and the “signal tube” of your Klarus function the same way as my humble C8’s. You could try to touch the blob at the end of the black lead on the leadboard with a pen probe connected to the “shell” of the light… In the C8 this shunts the driver, causing the led to burn on direct drive. If (big IF) the light burns, it’s probably something in the driver or a connection. If the light does not burn, it could be anything.

(very) Remote possibility, this happened to me just once. The copper core in one of the leads going to the led is broken.

The G20 is with a friend now,(he is an electronics guy but no experience to flashlight modding, btw) he says he cannot take out the driver as the switch is in the way or something.

Could anyone here chime in on how to do it?