This started about a year ago. Used to work fine. Typically when my furnace reached temperature the heat and blower would shut off until next cycle of heating.

Now it starts the same but the heat stops while the blower continues which causes cold air to be blown out for up to 10 minutes before the blower stops. What could be the main culprit of this?

Is something shutting the flame down before the furnace realizes it? Could it be anything with the electronic thermostat? I'm not afraid to replace elements of the furnace but no idea how to troubleshoot this to diagnose the problems.

Thanks for any help.

I'm not an expert, just a "Handy Guy", but this sounds like it could be an over-temperature limit switch triggering.
The cause can be several things--the easiest being a dirty air filter. At least this might give you something to start looking at.

If your thermostat is still calling for heat but the furnace cuts off, you might be on the right track with my suggestion.

Best of luck,
WallyH

Wow, I just saw your post was 5 days ago! Hopefully this has been resolved by now.