Thin films of FeCl3 doped polyalkylthiophene (side chain length from 6 to 18) have been automatically dedoped in ambient atmosphere at room temperature. The dedoping rate is dependent upon the side chain length, dopant, ambient lighting and film morphology. The maximum dedoping rate occurred in the first 30 min and dropped off rapidly after one hour. Dedoping is the reversible process of doping, bipolarons being reduced to polarons and then to the neutral state. The production of Fe2+ and HCl during the dedoping process indicates that moisture acted as the reducing agent. In other words, bipolarons were reduced by H2O to polarons. Polarons subsequently disproportionate to bipolarons and neutral polymer or reduced Fe3+ to Fe2+. Protons, produced from the oxidition of H2O, react with FeCl4- or FeCl42- to produce HCl and iron complexes.