I just replaced the thermostat last Saturday, and now there's heat! The blower upgrade just forced more cold air through the duct. I took out the old thermostat (was surprised to even see one there) and it was all gunked up. Wouldn't close less then 1/8 inch. So, new 195* thermostat and voila! HEAT! Well, you can't toast marshmallows with it, but it keeps me warm.