We have an older Tappan ANS Z21.47 furnace, circa 1979. When the cooler weather season started this year we turned on the heat and noticed that once the house had reached the correct temperature then the blower would remain on and blow cooler air for at least 20 minutes afterwards. We had read some posts that we should hit the furnace where the sensor is as sometimes it gets stuck. This worked a couple of times, but now we actually have to turn the furnace off at the switch to get it to stop. Or we have to wait it out and let it blow for 20 minutes. If we can fix this ourselves that would be great, but if we need to hire help it would be nice to know what it might be so they can't take us to the cleaners. LOL Any help would be greatly appreciated.

Thank you -

The Kenney's

Replace the defective sensor the you have been hitting this is usually the fan control. Parts available from your local HVAC shop.