How A Pressure Switch Problem Can Keep Your Furnace From Running

The pressure switch in your furnace is a vital part of its safety system. Yet when a pressure switch stops working the way it should, it can keep even a perfectly safe furnace from functioning. If you would like to improve your knowledge of this important component, read on. This article will discuss the role of the pressure switch, and the unintended problems it can cause.

Safe Venting

The purpose of the furnace pressure switch is to ensure that the draft motor is running before it allows gas to flow into the combustion chamber. The draft motor is responsible for pushing toxic exhaust byproducts out of your home through the vent pipe. When the draft motor is on, it creates a vacuum that sucks a rubber diaphragm on the pressure switch inward. This in turn triggers a switch on the gas valve, allowing gas to move through. Unless the pressure switch detects a vacuum, it will not allow gas to enter the combustion chamber.


Almost all pressure switch problems involve a failure to trigger the gas valve to open–even when the necessary vacuum is present. In some cases this is caused by a diaphragm that has become physically damaged. In others it may be the result of a physical blockage within the pressure switch. In such cases, a technician will need to either repair or replace the existing pressure switch.

If you believe that your pressure switch may be keeping your furnace from running, give the professionals at Metro Heating & Cooling a call 651-294-7798  at your soonest convenience.