What Happens When a Furnace Pressure Switch Goes Bad in Crane, IN?

When a furnace stops working, homeowners don’t usually suspect the pressure switch. In fact, many homeowners don’t even know what a furnace pressure switch does. What happens when a furnace pressure switch goes bad, and what causes a switch to fail?

Discover the answer below, then call us for heating services in Crane, IN.

Understanding Your Furnace’s Pressure Switch

All modern gas furnaces have a pressure switch designed to shut off combustion when the system detects negative pressure. Your furnace does this to prevent fires and a dangerous buildup of carbon monoxide in your home.

Depending on whether you have a single-stage or two-stage furnace, your system might have one or two pressure switches. There are also a few different kinds of pressure switches, including electronic and mechanical ones. Mechanical switches use tubes and pistons to detect problems, while electronic ones use sensors.

What Happens When a Furnace Pressure Switch Goes Bad?

As mentioned above, the pressure switch will shut furnace operation down when it detects negative air pressure. Negative pressure can occur if your home is too airtight, for example, if you’ve added too much insulation and weatherstripping to your windows and doors.

The laws of physics don’t like negative air pressure, so the condition will try to correct itself however possible. That means exhaust gases will flow back into your home instead of outside where they belong — a phenomenon called backdrafting.

Normally, when a pressure switch detects negative air pressure and backdrafting, your heating system will enter furnace lockout mode. You won’t be able to use the system until you resolve the problem.

But what happens when a furnace pressure switch goes bad? If your pressure switch fails, your furnace will keep on doing its thing as though nothing is wrong. Dangerous levels of carbon monoxide can build up in your home to the point that they sicken you or spark a fire.

If your pressure switch is faulty but not completely broken, you might also notice the furnace not igniting and short cycling. When this happens, your furnace will keep turning on and off again at random.

Furnace Pressure Switch Troubleshooting for Crane, IN, Homeowners

Why do furnace pressure switches break? The most common cause is old age. Pressure switches last about 10 years before they fail, while the average furnace lifespan is about 15 to 20 years. So, if your furnace is nearing its 20th birthday and you’ve never replaced the pressure switch, it’s probably on its last legs.

A dirty pressure switch hose might also be to blame for your malfunctioning switch. Over time, these hoses can clog with debris and water, which can cause the pressure switch to stop working. The same can happen if your pressure switch hose becomes damaged or too loose.

What happens when a furnace pressure switch goes bad? The diaphragm in your pressure switch provides another potential point of failure. The diaphragm handles the air supply of the pressure switch. If the diaphragm becomes cracked, the switch will stop working.

What Should You Do if Your Pressure Switch Fails?

Knowing that your pressure switch has failed can be difficult because your furnace might not alert you to the problem. The only sign you may notice is the blaring sound of your carbon monoxide alarm or your furnace short cycling.

If you think your pressure switch has quit working, shut off the furnace immediately, call us for help, and don’t use the system again until we fix the problem. Using a furnace with a broken pressure switch is dangerous and can lead to fires, explosions, or carbon monoxide poisoning.

Whatever you do, don’t attempt to repair the pressure switch yourself. Homeowners can DIY some furnace maintenance tasks, but pressure switch repair is not one of them. It’s better to be safe than sorry and leave pressure switch repairs in the hands of an expert.