Your furnace is very important - and if it is going to fail, you can be sure it will do so on the coldest day of the year. It's important to be aware of signs that your furnace is failing before it dies altogether, so you can call the technician before you are left in the cold. Here are some signs that your furnace will need some repairing.
1. There is more dust coming out of the vents. This means your furnace is not cleaning the air properly. It might mean you just need to change the filters, but if that doesn't work then there is something more serious going on.
2. Your furnace is 20 years old or more. Very few furnaces last past the 20-year point.
3. The furnace is blowing cold air from one or more vents. This is definitely a signal that you need to call the technician now before it starts blowing cold air from all the vents. It's most likely the blower fan.
4. Unusual noises. You know how your furnace is supposed to sound. If it starts making noises that aren't familiar, it's likely there's something loose.
5. Yellow pilot light. Call the technician immediately - this only happens if you have a carbon monoxide leak. Also, if your carbon monoxide detector goes off, you should always call a technician right away. Other signs of a carbon monoxide leak include rusting on flue pipes, soot around the furnace, and increased condensation.
6. You keep having to adjust the thermostat. It might be you - or it might be that your furnace is not keeping a stable temperature.
7. Your heating bill is creeping upwards even though the weather is the same. This is likely to be your furnace, although you might also want to check your insulation.
Fixing your furnace before it fails is always better than waiting before it's too late and gets very cold.