If your furnace stops working, here are some key things to check before calling a professional:

1. Thermostat Settings: 

         Ensure the thermostat is set to "heat" and is set to a temperature higher than the current  room temperature.Check the battery if it has one, as a low battery can cause the thermostat to stop working.

2. Power Supply:
         Make sure the furnace is getting power. Check the breaker box for any tripped circuits and reset them if necessary.Some furnaces have a dedicated switch that looks like a light switch; make sure it’s in the "on" position.

3. Air Filter:
        A clogged air filter can restrict airflow, causing the furnace to shut down. Check if the filter is dirty and replace it if necessary.

4. Gas Supply (for gas furnaces):
        Ensure the gas valve is open and that there's a gas supply. If there are any signs of a gas leak, turn off the furnace immediately and contact your gas company.

5. Pilot Light or Igniter:
       Older furnaces with a pilot light should have it lit. If it’s out, follow the manufacturer's instructions to relight it safely.
Newer models use an electronic igniter; if the igniter is faulty, it may need to be replaced.

6. Furnace Door:
       Some furnaces have a safety switch that won’t allow them to run if the door isn’t securely closed. Check to make sure the access panel is properly closed.

7. Blocked Vents:
      Check for any blockages in the furnace's intake or exhaust vents outside. Snow, debris, or ice buildup can obstruct airflow.

If these steps don’t help, there could be an internal issue that requires a professional HVAC technician from glorsheating.com to diagnose and repair.