[halapeno]

Even with the system turned off at the thermostat, the blower turns on about once an hour for about 5 minutes. I replaced the thermostat, but still have the same symptoms. Otherwise, both the heat and AC work well. Anyone have a clue why the blower wants to cycle without heat or AC?

[kooler]

You didn't list a brand or model number for your system so one can only guess what you're dealing with... There is a control that will cycle the blower that measures the temp inside the heating chamber called a fan limit switch... Generally it's designed to only turn the blower on when the chamber is hot/warm (during the heating mode) so it's possible this control is malfunctioning and cycling the blower when the chamber is cool... Suggest locating and inspecting/replacing this fan limit switch...