When your home's furnace doesn't work, it can be good to leave major repairs to a professional, especially if the repairs may involve gas lines. Not performing those repairs properly can mean a gas leak that can be very dangerous for you and your home. However, some repairs are somewhat simple and you may be able to manage them yourself with a few tools and a bit of know-how. Note a few of those here so you can address them, or at least know what to expect by way of repair bills if you do need to call a contractor.
1. No air being blown
If you hear the furnace come on but no air comes out of the vents, this can be a problem with the pulley belt between the motor and the blower. You can often replace a broken or worn pulley belt yourself; first remove the front door to the furnace and locate the belt between the motor and the blower. You want to check the manufacturer's codes on it to find a replacement pulley belt. Once you've purchased a replacement, slip it over the motor pulley, which is typically much smaller than the blower pulley, and then gently guide it with one finger over the blower pulley. This should allow the blower to come on when the motor is engaged, and you'll get hot air in your rooms again.
2. No heat
If the motor to the furnace doesn't come on at all, it may have shut down due to an overload. If you've been running the furnace nonstop for several hours, this may be the culprit. There should be a reset button near the front of the motor or blower; you can press this and note if the motor comes back on. If the motor still doesn't come back on, call a contractor to note if the motor has simply burned out and needs replacing.
3. Blower runs continuously
There is a limit switch on the furnace, just below the plenum; the plenum is the box at the top of the furnace that distributes warm air to the home. If the limit switch is broken, the blower will run continuously, even if the space gets warmer than the setting on the thermostat. Check this limit switch to ensure that it's on; if so, you may need to have it replaced so the blower will shut off as it should. If the limit switch is not the issue, your home's thermostat may need to be replaced or the wiring connecting it and the furnace may need replacing, so the thermostat can properly communicate the desired temperature to the furnace.
For help fixing your furnace, contact a company like heating by Thermax Refrigeration & Heating Ltd.