sghera64
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About 18 months ago I bought the JBJ True Temp Digital Heater Controller. I was quite happy with it until recently when the displayed temperature reading on the controller started to “drift” downward away from the actual water temperature. This created a problem because the controller started to turn the heater on when the tank temperature was already a little warm.
Reading the instruction manual, I discovered that the JBJ True Temp controller can be calibrated against a known standard. I did that, but in a few days, the temperature drifted downward again. Eventually, I hit the calibration adjustment limit.
I quick autopsy of the thermal probe revealed that, mechanically, the integrity of the probe and thermistor were okay - - no water had visibly entered the internal wiring. Checking the resistance of the thermistor revealed that it is a Type III 10K Ohm thermistor, but was *way* off the mark of resistance/temperature specification.
I emailed JBJ Lighting for help. Within 10 minutes, they responded with a tech support phone number for me to call [310-672-0480 out of California]. Tech support was not at all surprised that after 18 months the temperature drifted. They told me that the thermal probe must be replaced every 9-12 months - - as a matter of fact. Thinking I had “missed something”, I re-read the entire instruction book - - including the troubleshooting and periodic maintenance parts. There is no mention of this. But - - it makes sense to me. So, I ordered two replacement thermal probes from them for $15 each. Seemed cheaper than buying a new JBJ for $90. I already have an InkBird ($35), but my InkBird cannot be calibrated and it does have the same temperature dead-band of +/- 1(F) as the JBJ Controller.
Bottom Line: if you have a JBJ that has experienced temperature drift and have not discarded it, you might “restore” it by replacing the thermal probe. If your JBJ controller has not drifted (yet), you might consider ordering a replacement probe from JBJ. I wonder if BRS or Premium Aquatics might consider stocking these.
Side-note: After figuring out the specs on the thermistor (10K Ohm, Type III), I ordered a 50-pack of these thermistors on Amazon for $10. I soldered a new thermistor onto the old thermal probe lead wire, inserted it into some Tygon tubing and put a very thin layer of silicon over the exposed tip of the thermistor (E.g. DIY replacement probe). Ha! It’s working. I calibrated it and have been checking the calibration e/o day against a NIST thermal probe. So, if you are handy, there is a $0.20 fix. I have no idea how long my design will keep the water out of the probe. Once water gets in and shorts the wiring, the resistance will plummet, the “apparent” temperature will sky-rocket and the heater will not be triggered to heat - - even if tank temp is low. That is, if this happens in winter, my tank will slowly cool, my 300W InkBird controlled heater alone will not be enough to maintain temp and the InkBird audible alarm will alert me.
My hope in sharing this is that others who have - - or are considering buying - - a JBJ Controller know that:
Reading the instruction manual, I discovered that the JBJ True Temp controller can be calibrated against a known standard. I did that, but in a few days, the temperature drifted downward again. Eventually, I hit the calibration adjustment limit.
I quick autopsy of the thermal probe revealed that, mechanically, the integrity of the probe and thermistor were okay - - no water had visibly entered the internal wiring. Checking the resistance of the thermistor revealed that it is a Type III 10K Ohm thermistor, but was *way* off the mark of resistance/temperature specification.
I emailed JBJ Lighting for help. Within 10 minutes, they responded with a tech support phone number for me to call [310-672-0480 out of California]. Tech support was not at all surprised that after 18 months the temperature drifted. They told me that the thermal probe must be replaced every 9-12 months - - as a matter of fact. Thinking I had “missed something”, I re-read the entire instruction book - - including the troubleshooting and periodic maintenance parts. There is no mention of this. But - - it makes sense to me. So, I ordered two replacement thermal probes from them for $15 each. Seemed cheaper than buying a new JBJ for $90. I already have an InkBird ($35), but my InkBird cannot be calibrated and it does have the same temperature dead-band of +/- 1(F) as the JBJ Controller.
Bottom Line: if you have a JBJ that has experienced temperature drift and have not discarded it, you might “restore” it by replacing the thermal probe. If your JBJ controller has not drifted (yet), you might consider ordering a replacement probe from JBJ. I wonder if BRS or Premium Aquatics might consider stocking these.
Side-note: After figuring out the specs on the thermistor (10K Ohm, Type III), I ordered a 50-pack of these thermistors on Amazon for $10. I soldered a new thermistor onto the old thermal probe lead wire, inserted it into some Tygon tubing and put a very thin layer of silicon over the exposed tip of the thermistor (E.g. DIY replacement probe). Ha! It’s working. I calibrated it and have been checking the calibration e/o day against a NIST thermal probe. So, if you are handy, there is a $0.20 fix. I have no idea how long my design will keep the water out of the probe. Once water gets in and shorts the wiring, the resistance will plummet, the “apparent” temperature will sky-rocket and the heater will not be triggered to heat - - even if tank temp is low. That is, if this happens in winter, my tank will slowly cool, my 300W InkBird controlled heater alone will not be enough to maintain temp and the InkBird audible alarm will alert me.
My hope in sharing this is that others who have - - or are considering buying - - a JBJ Controller know that:
- The temperature display on these can be calibrated [very cool and appreciated by me].
- The thermal probe should be replace every 9-12 months by calling JBJ Lighting [310-672-0480 out of California].
I had the jbj as well and my biggest issue was the silicone on the temp probe where the wire goes in would always crack and break off.
