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3 Steps Necessary To Resolve A Furnace Pressure Switch Fault

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One of the advantages of hiring a professional to deal with your heating issues is knowing that you're getting an accurate and permanent fix the first time. It's often too easy to read an error code from your furnace, replace a part, and find that the problem still exists or returns very quickly. The best option is to use these error codes as a starting point for further diagnosis.

If your furnace is currently throwing a pressure switch fault code, you shouldn't assume that the problem is your draft inducer motor or the pressure switch itself. Professional technicians will typically run down a long list of diagnostic steps to confirm the situation when confronted with these issues. Here are just three steps necessary to find the actual cause of a pressure switch fault.

1. Check for Internal Wiring Faults

If the internal wiring in the pressure switch fails, it can create a short between the connecting terminals. A wiring short will prevent the switch from operating correctly, and the furnace will typically fail to ignite at all. The best way to check for the presence of an internal wiring problem is by using a multimeter to confirm that there's no continuity between the terminals on the pressure switch connector.

If your technician finds a short between the terminals, it's a good sign that the switch is faulty and requires replacement. However, detecting no continuity while off doesn't guarantee that the switch is good. Instead, additional diagnostic steps are still needed to confirm that the system is operating correctly.

2. Measure Exhaust Pressure

Another handy tool used in this diagnostic process is a manometer. Every pressure switch requires the exhaust inducer motor to produce a specific pressure differential. If this negative pressure doesn't exist, the pressure switch will not close, and the furnace won't turn on. A manometer can measure pressure, allowing a technician to confirm that the inducer is working as it should.

If there's sufficient pressure to close the switch, the most likely culprit is a faulty pressure switch. On the other hand, insufficient pressure may have numerous potential causes.

3. Check Exhaust Path

The most common cause for insufficient exhaust pressure is an obstruction in the exhaust flue. Animals can sometimes become trapped in exhaust pipes, where they ultimately cannot escape. Other blockages, such as bird nests, can also prevent the draft inducer from creating adequate pressure for the switch to close.

Before moving on to more in-depth steps, HVAC technicians will always confirm that the exhaust path is clear and provides adequate ventilation to the outside environment. At this point, they can finally move on to checking the draft inducer motor itself, but only after ruling out all over simpler and cheaper solutions.

If you are in need of heating repairs, contact a professional in your area.