katakow2 - I agree with new mum; it worked that way with both my dd & ds. DD is 19 months now, too, has been on 1 nap for a little while, 1.5 hrs. It's slowly been moving a little later (she kept the am nap). DS also kept his am nap, and it seemed to take a while for his nap to move back a bit (now it's around 12:30pm/1pm), and he's almost 3. I also remember that it took a while for his nap to extend to 2 hours. Everyone's different, but that was my experience with them.
Lena, also agree that if you could keep the 2 naps at this age, that'd be optimal! not to ask a stupid question, but he's not teething or anything like that, is he? I know my ds went through teething (molars) around then and absolutely refused naps, crying & all, which was really unusual (he was an angel baby). Turned out his molars were coming in and when we helped him with the pain/discomfort, he slept well.