Furnace Pressure Switch Problems in Cornwall & SDG
Is Your Furnace Showing a Pressure Switch Error?
A furnace pressure switch fault is a common reason a gas furnace may fail to ignite or suddenly stop producing heat. If you live in Cornwall, Ontario or the surrounding SDG area and your furnace starts but the burners never come on, you may be dealing with a pressure-switch or venting-related problem.
At SDG Duct Cleaning, we're HVAC technicians with experience diagnosing residential gas furnaces. One important thing we've learned over the years is that a pressure switch error does not automatically mean you have a bad pressure switch.
The pressure switch is part of the furnace's safety system. When it doesn't operate as expected, the furnace control board may prevent the ignition sequence from continuing.
Understanding why the pressure switch isn't closing or opening properly is the important part.
What Does a Furnace Pressure Switch Do?
When your thermostat calls for heat, your furnace goes through a specific sequence before allowing the burners to ignite.
One of the first components you'll normally hear start is the draft inducer motor.
The inducer creates the draft required to safely move combustion gases through the furnace heat exchanger and venting system.
The furnace pressure switch is used to prove that the required pressure condition has been established.
Once the furnace control board sees that the pressure switch has operated correctly, the furnace can continue through its ignition sequence.
If that doesn't happen, the furnace may stop the sequence and display a pressure switch fault or error code.
What Are the Signs of a Furnace Pressure Switch Problem?
One of the most common symptoms is a furnace that attempts to start but never actually lights.
You might notice:
- Thermostat is calling for heat but there's no heat
- Furnace inducer motor starts but burners don't ignite
- Furnace repeatedly attempts to start
- Furnace starts and then shuts down
- Furnace eventually goes into lockout
- Furnace control board flashes a pressure-switch error code
- Furnace works intermittently
- Furnace stops operating during cold or windy weather
- Water or condensation is present around the furnace or venting
The exact symptoms depend on the furnace and what's causing the pressure-switch circuit to fail.
Does a Pressure Switch Error Mean the Pressure Switch Is Bad?
No.
This is one of the most important things for homeowners to understand.
If your furnace displays a pressure-switch code, the pressure switch itself could be defective.
But replacing the switch simply because the furnace displays a pressure-switch fault can result in replacing a perfectly good part.
The furnace may actually be telling us:
“I'm not proving the draft condition I need to safely continue operating.”
The next question is why?
What Causes a Furnace Pressure Switch Fault?
There are several possibilities.
Blocked Furnace Intake or Exhaust Vent
This is particularly important during an Eastern Ontario winter.
Snow and ice can obstruct furnace intake or exhaust piping. Leaves, debris and other obstructions can also cause problems.
If your furnace suddenly stops working after heavy snowfall, checking the outside furnace venting for an obvious obstruction is one of the first visual checks a homeowner can make.
Do not reach into, dismantle or modify the furnace venting yourself.
Condensate Drainage Problems
High-efficiency furnaces produce condensation.
If the condensate system becomes blocked or isn't draining properly, water can interfere with the furnace's ability to establish the pressure required for operation.
Depending on the furnace, this can involve the condensate trap, drain tubing or other drainage components.
Pressure Switch Tubing
Small tubing connects the pressure switch to the furnace's pressure source.
If that tubing becomes blocked, cracked, loose or filled with moisture, the pressure switch may not receive the pressure it needs to operate correctly.
Inducer Motor Problems
Sometimes what appears to be a pressure-switch problem actually begins with the furnace inducer motor.
If the inducer isn't creating sufficient draft, the pressure switch may simply be doing exactly what it was designed to do — preventing the furnace from continuing its ignition sequence.
The inducer itself, inducer wheel, venting or another part of the draft system may need to be investigated.
Blocked Pressure Port
The small port used to communicate pressure to the switch can sometimes become restricted.
This can prevent the switch from properly responding even though other furnace components appear to be operating.
Venting Problems
Improperly installed, restricted or damaged furnace venting can also contribute to pressure-switch faults.
This is another reason we don't recommend automatically replacing a pressure switch based solely on an error code.
Failed Pressure Switch
And yes, sometimes the pressure switch really has failed.
The switch can eventually become defective and fail to operate at the required pressure.
But that's something we want to determine through proper furnace diagnostics rather than guesswork.
Why Does My Furnace Inducer Run but the Burners Don't Light?
This is a very useful symptom to tell your HVAC technician about.
You may hear a smaller motor inside the furnace start after the thermostat calls for heat. That's often the draft inducer.
But then nothing else happens.
Depending on the furnace, a pressure-switch or draft-proving problem is one of the things we may investigate.
The furnace may be waiting for the pressure switch to prove the proper condition before allowing the ignition sequence to continue.
That doesn't establish the diagnosis by itself, but it gives us an important clue about where the furnace is stopping in its sequence of operation.
Furnace Pressure Switch Problems During Cornwall Winters
Our climate can create some additional problems for high-efficiency furnaces.
Homes throughout Cornwall, Long Sault, Ingleside, Lancaster, Williamstown, Martintown, Apple Hill and the surrounding SDG area can experience significant snow, freezing temperatures and wind during the heating season.
Outdoor furnace intake and exhaust terminations therefore deserve particular attention.
If a furnace suddenly stops heating during or immediately after a major snowfall, an obvious snow or ice obstruction outside is worth looking for from a safe location.
However, if the venting appears clear and the furnace continues displaying a fault, the system should be properly diagnosed.
Can You Bypass a Furnace Pressure Switch?
A furnace pressure switch should not be permanently bypassed to make a furnace operate.
It's a safety control.
Jumping out a safety device doesn't repair the condition that caused the furnace to stop operating.
If the pressure switch isn't proving the required condition, we want to determine why it isn't proving.
That's the difference between diagnosing a furnace problem and simply trying to make the burners come on.
Furnace Pressure Switch Diagnosis in Cornwall, Ontario
If your furnace isn't working and you suspect a pressure switch problem, you don't need to diagnose it yourself.
Tell us what you're seeing or hearing.
For example:
“The furnace starts but doesn't light.”
“The inducer runs but I don't get any heat.”
“The furnace is flashing a pressure-switch code.”
“The furnace keeps trying to start.”
Those details can help us begin diagnosing the problem.
SDG Duct Cleaning provides furnace repair in Cornwall, Ontario and surrounding SDG communities during our regular service hours. We're HVAC technicians, and our goal is to determine what is actually preventing the furnace from operating before recommending a repair.