Most furnaces rarely make a sound. They rarely smell too, except when you first fire them up in the late fall. That is advantageous, because the minute your furnace starts behaving like a broken-down steam locomotive, you know you have problems. If your furnace behaves in any of the following fashions, you need to call a furnace repair service. 

It Clanks Like the Clickety-Clack of Steam Engine Wheels

A furnace should never sound like a train's wheels. There is clearly something loose and flying around inside the appliance if you hear any such noise. Usually, it means that some part of the blower fan has broken off and is regularly being smacked around inside the furnace by the rest of the fan whirring past it. Your repair technician will have to shut off the furnace, open up the access panels, remove the broken parts, and replace the blower fan with an entirely new blower fan. (You cannot really reattach the part of the fan that broke off because it will not stay on once the fan starts spinning again.)

It Smells Like Burning Oil Non-Stop or Like Burning Wood/Carbon Fuel Like the Engine of a Train

Your furnace definitely should not smell like burning wood or coal (unless it is one of those furnaces, but that is most unusual). It should also not smell like burning oil past the first day that you have fired it up. If you have an electric or gas furnace, it should not smell like any of the above at all!

Additionally, any home that smells of rotten eggs when the furnace tries to kick in is in serious danger of blowing up. All of the above spell problems with something burning and/or leaking that should not be burning and/or leaking inside your furnace. The technician will have to find what is burning, remove it, and replace it if it is actually a part of the appliance that has fallen off and is burning. Otherwise, the technician will have to find the leak for oil, gas, or propane, and fix the leak. 

It Is Not as Hot as It Should Be 

Steam engines had to burn incredible amounts of fuel to create enough heat and steam to propel massive tons of steel forward. Engineers would sweat off half their body weight from working in the engines and feeding the hot boxes. When engines broke down and did not get as hot as they should, you could tell that the trains were busted. The same holds true for furnaces. If your furnace is not producing enough heat, there is something wrong with the ignition switch or the burner. Both need correcting and repair. 

For more information, contact a furnace repair service in your area.