I have a Honeywell thermostat that was included with my home when it was built in 2006. Today I went to turn my heat on and noticed it did not turn on no matter how high I set the temperature. I have noticed a slight rattling come from the vent downstairs when the air or heat is on but didn't pay attention to it. I thought this might be the cause and that some wires may have shorted, but when I turned on the fan it worked fine (still with the same rattling). Any idea why my heater is not turning on?

((Today I went to turn my heat on and noticed it did not turn on no matter how high I set the temperature))

Is your house still under warranty?
If so call the builder/HVAC people.

If not call a qualified contractor. The noise you are hearing is not normal and something has happened to your heating unit.

There could be many different items that cause your furnace not to turn on and since you are having the noise problem it is best to have a professional look it over.