I have a Trane heatpump and A/C system (gas/electric) controlled by a Trane weathertron XT 500 programmable thermostat. I have an air intake directly above my woodstove in my basement so that I can run the fan on my system to blow the warm air throughout the house (without actually using the heatpump). When I switch the thermostat over from "auto" to "fan on", sometimes the fan starts, but other times it does not (and no tinkering with the settings will start it). I haven't figured out how to get the fan to consistently come on. I've tried this with the thermostat set to Off, Heat, and Cool. Everything works fine in the "auto" setting. Suggestions?