Whirlpool AD40USL Dehumidifier

At first this dehumidifier seemed to work great - it took the moisture out of the air in my basement very effectively. Unfortunately it wouldn't stop. The basement was bone dry (humidity about 30% according to an electronic hygrometer), but no matter what level the humidifier controls were set to, it wouldn't ever cycle off. I returned the unit to Lowe's and exchanged it. The second one (same model) had the same defect, so I returned it for a refund. No matter what the controls say, this thing has only two functions: ON and OFF. I'm tired of carrying these things back and forth, and I'm going to try another brand.