Pavel was clear, efficient, and explained/illustrated the problem with the unit that wasn't working was due to dust and mold in the blower. The other two units probably have the same problem but they are working fine right now and the price is VERY high so we will have to call again if we have problems with the other two. I'm not sure why the units should have mold, but when Pavel showed me the blower it was clear he was right! Good workman. He was fast, friendly, thorough!