Why Won’t My Gas Furnace Start on the First Try?

After a period of time, most homeowners become familiar with how their gas furnace normally functions and sounds. So it is a bit disconcerting when a homeowner notices that their formerly functioning furnace now takes two or three “tries” before it finally ignites and begins to actually heat their home. In this post, we will discuss how this error occurs and what to do about it.

Why Won't My Gas Furnace Start on the First Try?

The Ignition Sequence

When the temperature inside a home is lower than the thermostat temperature, the thermostat sends a signal to the furnace to begin the ignition process. Before a gas furnace will begin blowing heat, it goes through a series of checks to determine if the furnace is functioning normally enough to begin the heating process.

As part of this process, a component called a “pressure switch” will close, thus allowing electrical current to pass, which in turn allows the gas inside a furnace to ignite and begin the actual heating process.

When it Goes Wrong

Normally a homeowner might hear a “click” coming from their thermostat which means the thermostat is sending a signal to the furnace. Shortly after, the furnace will begin to sound as if it will soon begin its job of distributing hot air throughout the home. Sometimes during this process a pressure switch may become stuck, thus stopping the furnace from going further. The furnace will act as if it stopped, only to begin the process all over again in a few minutes. It may take several “tries” before the furnace actually starts completely and begins to force heat throughout the home.

The reasons behind an improperly functioning switch are many. In some cases, there could be debris impeding the switch from completing its function. In other cases, there might be faulty wiring causing the issue. Sometimes the issue stems from a faulty pressure switch which needs replacement.


Whatever the reason for the malfunction, problems with a pressure switch are best left to the professionals. If your furnace is trying and failing to start on the first try, please contact us. We can help!

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