If your furnace is making a weird noise or your heat has stopped working, you might be ready to grab your toolbox and see what's wrong. However, it pays to take a step back and evaluate the situation. Some furnace problems are well within the realm of a handy DIYer, but many furnace failures should be left to trained professionals. Whatever your furnace's power source happens to be, it is a complex appliance that can break down in a variety of ways. Attempting repairs can sometimes lead to costlier problems down the road or even place you into a dangerous situation if you don't know what you're doing.
Fortunately, it is relatively easy to recognize when you might be in over your head. If you notice any of these three situations, put down the toolbox and call a professional.
It should probably go without saying, but never attempt to repair or diagnose a gas leak yourself. Natural gas is odorless, but gas leaks are so dangerous that a special chemical is added so that they can be detected by smell. If you smell gas, then it's time to call your gas company immediately. If you know where the gas shut off is in your home, shut the gas off as soon as you smell an unusual odor, then open any nearby windows and doors. Once you have done this, leave the house until professional help can arrive.
Heat Exchanger Cracks
If you have a gas furnace, then the burner doesn't directly warm the air in your home. The natural gas combustion process produces carbon monoxide, an incredibly dangerous substance that can be lethal in even relatively small quantities. To protect you from this combustion byproduct, heat is produced in a sealed chamber that exhausts to the outside environment. The heat exchanger is responsible for transferring energy from the exhaust gases to the air handler which then distributes it to the rest of your home. A cracked heat exchanger is a dangerous situation, so it is important to immediately stop using the furnace and call for back-up from a professional.
Failure to Ignite
In the past, a furnace that wouldn't ignite was often suffering from a failed pilot light. Modern furnaces are more energy-efficient and use electric ignition systems. While electric igniters are durable, diagnosing problems with them may be more difficult. A furnace that won't ignite is not often dangerous, but determining the root cause can be challenging and the potential exists to cause more damage while you are attempting to fix the existing problem. If your furnace won't start, get in touch with a qualified furnace repair company.
If a problem is beyond your capability, the smart move is to bring in furnace repair services.