KEL103 Temp Control Issue - Looking for advice.

[rfdes]

Hi -
I own a Korad KEL103 electronic load that has served me well with no known issues.  Until today.

I've discovered an issue with the temperature control circuitry.  I've been testing some 18650 batteries and running a low power capacity test where I never exceed a 2W dissipation.  I would think that the fan would never come on but after about 5 hours of running the battery test at 2W the fan comes on.  No big deal but then fan never shuts off even after an excessive cooling period..  At the conclusion of the test (another hour or so) I disable the load (ON/OFF) and only then does the fan turn off.  Enabling the load to ON, the fan does NOT come back on.  So, it seems that the thermistor properly kicks on the fan when needed, the fan does it's job but the fan is not disabled.

I've heard other users claim that the fan would cycle every minute or so when cooling.  I'm sure that if I was maxing out the load at 300W, I would expect the fan to stay on constantly but not at 2W.
Anybody seen this issue before and know of the remedy?
Thanks
Jim

[Gediminas]

I have Tenma (rebranded kel-103), it does same thing after long period of use. I think it is programmed to do that just to remove some heat from power supply.
Otherwise it is cooling by switching on and off like you said.

[t1d]

Kind of sounds like a firmware issue? Maybe reflash the firmware, even if you have the current version. If that is not the cure, you are probably going to have to dig into the circuitry. Maybe the thermocoupler is held high, or low, and that resistor has failed? Maybe the thermocoupler is bad? Maybe the microcontroller is failing? HTH.