CO2 AQE v2 Reporting Constant Nonzero Value


I’ve got a CO2 egg that has worked great for ~2 months now, but the past few days it has been broadcasting a constant nonzero value. Any thoughts? Image below shows the sensor flat line at ~830 ppm.

Power cycling the egg has not resolved the issue.

First instinct is a sensor hardware problem.



Hi @NT1, interesting, was there anything contextually noteworthy surrounding this change in behavior? I just downloaded the last 5 hours of data. and it’s not entirely flat-lining, there was some kind of spike from 943 ppm to 1252 ppm at around noon eastern time today, but it’s been flat at 943 for the last few hours, which is strange. The temperature and humidity reports seem to be exhibiting normal variation… It might be worth looking at the serial monitor output to see if anything unusual is being printed to the screen that might indicate a hardware fault. You might also try breathing into it heavily for a minute to see if the CO2 numbers shoot up.


Not that I’m aware of, but the sensor is in a remote location at the moment so I can’t say for certain. It was moved to another location around noon today.


Gotcha, I can’t entirely rule out a software problem, but I generally agree with your intuition given that it was working fine for a long period of time and then started experiencing a behavioral change. It looks to me like the firmware will, in fact, report the same value over and over again if it can’t get a new value from the sensor, but that doesn’t tell us very much about why it can’t get a new value.


Is there some way I can test the sensor?

Or open the egg up and install a replacement sensor? I’d like to try to troubleshoot a bit before going here though…


The only way I can think to test the sensor, per se, would be to load an test program onto the Egg using Arduino, and I don’t have one handy to point you to at the moment unfortunately.

I would advise that for repairs you should probably send an Egg back to us rather than trying to do an in-place repair / replace operation yourself. For the CO2 I Egg, I believe there are four wires connecting the sensor board to the processing board (rx, tx, gnd, and 5V), and they are soldered to the respective boards on both ends if I recall correctly.


I can do that too, just let me know how best to proceed.


We are closed next week, but yea I would say if it doesn’t self correct, your best bet would be to send it back to us for evaluation and repairs as needed. If we need to replace the CO2 sensor, I would estimate it will cost about $100, but lets see what we see. You can ship the unit back to us at the address displayed in right hand sidebar of


Sure, that works. Any documentation or reference numbers I need to send along with it?


Good point, I’ll private message you a RMA #.