I am having the same problem. I am using a programmable thermostat and I noted that the thermostat is supplying voltage intermittently to the furnace during the off time. I think the spike is just long enough to turn on the blower and then it shuts off. Again it only does this in the cooling phase and runs normal when heating when the temp drops below values.
I think this is a conspiracy to keep selling thermostats. I have fixed the problem with a new thermostat only to have it happen again just as the warranty kicks out.
If you found it was something else I would like to know.
