I have now had twice the same problem with ADS1015. First with a machine soldered board and now with a Adafruit module. I use the chip with Adruino Mega 2560 R3 and 5V supply voltage.
I connected 3V to analog input 0 and ran the single ended example from Adafruit. That channel shows a reading close to zero (0,,,3). It should show much more. I have used Nick Gammons I2C spy and it finds the chip at 0x48 as it should.
I have no idea... I don't know what a ADS1015 is (and I didn't bother Googling)… But, Adafruit is one of the more reliable sources of information. And, I believe they have their own forum.
Time to post the code AND a real picture of the setup.
The ADS1015 and it's bigger brother the ADS1115 are commonly used here without problems.
You did ofcourse connect ground of that 3volt source to ADS ground...
Leo..
Last night I remembered that there was a temperature sensor on the same bus. It was on a other board, so it was easy to forget. It didn't show on I2C bus spy output either. When I took that sensor away ADC started to work.