Nordyne Furnace Pressure Switch Open: Causes, Diagnosis, and Fixes

The Nordyne furnace pressure switch open fault is a common safety-related error that prevents ignition when the furnace detects improper venting or inducer operation. This guide explains what the pressure switch does, symptoms of a pressure switch open fault, step-by-step diagnostics, common causes, practical fixes, parts, costs, and when to call a professional. Safety-first advice and clear troubleshooting steps help homeowners and technicians resolve this issue efficiently.

Issue	Likely Cause	Quick Action
Pressure Switch Open Fault	Blocked vent, faulty switch, bad inducer motor, loose hose	Inspect venting, check inducer, test switch continuity
Intermittent Fault	Weak inducer, condensation, wiring issue	Run multiple cycles, inspect wiring, replace weak parts

What The Pressure Switch Does In A Nordyne Furnace

The pressure switch is a safety device that confirms the inducer motor and venting system are moving combustion gases properly before the furnace ignites. It senses negative or positive pressure through a small vacuum hose and closes an electrical circuit when conditions are correct. If the switch remains open, the control board will prevent ignition to avoid dangerous combustion or venting problems.

Common Symptoms Of A Pressure Switch Open Fault

Recognizing the symptoms helps pinpoint whether the fault is truly the pressure switch or a related system issue. Typical signs include repeated ignition attempts with no flame, an error code or LED indicating “pressure switch open,” the inducer fan running without ignition, intermittent operation that resets after cycling power, and visible obstruction of vents or chimney.

Why A Nordyne Furnace Shows “Pressure Switch Open”

Several conditions cause the pressure switch to remain open: blocked venting restricting airflow, a failed or sticky switch, cracked or disconnected vacuum hose, malfunctioning inducer motor, control board relay issues, or improper pressure settings. Less common causes include condensate buildup in high-efficiency units or barometric damper problems in older systems.

Safety Precautions Before Troubleshooting

Always turn off power to the furnace at the service switch or breaker before inspecting internal components. Shut off the gas supply if testing ignition components or opening the burner compartment. Use a multimeter rated for HVAC work, and avoid touching hot surfaces. If uncomfortable with electrical or gas systems, contact a licensed HVAC technician.

Tools And Parts Needed

• Multimeter (for continuity and voltage)
• Manometer or digital gauge (for accurate pressure measurement)
• Screwdrivers and nut drivers
• Replacement pressure switch (OEM or compatible Nordyne part)
• Replacement inducer motor or capacitor (if needed)
• Vacuum hose and clamps
• Shop vacuum or brush for vent cleaning

Step-By-Step Diagnostic Checklist

Visual Inspection

Inspect the venting and air intake for visible blockages such as bird nests, debris, snow, or ice. Check the small vacuum hose connected to the pressure switch for cracks, disconnects, or moisture. Look for corrosion, soot, or loose wire connections at the switch and control board.

Listen And Observe The Cycle

Turn the furnace on and watch the sequence: thermostat call, inducer motor starts, pressure switch should click closed, then ignition. If the inducer runs and the pressure switch does not close, note whether the inducer sounds weak or irregular. Record any diagnostic LED codes displayed by the control board.

Test The Vacuum Hose

Disconnect the hose from the pressure switch and briefly blow into it to confirm it’s not blocked. Replace cracked or clogged hoses. If moisture or condensate is found, allow drying and inspect the condensate trap or drain lines for obstructions.

Measure Switch Continuity

With power off, disconnect the pressure switch leads and test for continuity with a multimeter while inducing the correct pressure (using the inducer motor running). The switch should show continuity when proper negative pressure is present. No continuity with correct pressure means the switch is faulty.

Check Inducer Motor Performance

Verify the inducer motor runs at full speed and produces steady airflow. A weak motor or failing capacitor may spin slowly and not develop the required pressure to close the switch. Replace the inducer motor or capacitor if RPMs or airflow are below specifications.

Measure Actual Pressure

Use a manometer to measure the vacuum at the pressure switch port while the inducer is running. Compare readings to Nordyne specifications in the furnace manual. If pressure is below spec, check vent restrictions, inducer performance, and any in-line restrictors or dampers.

Common Fixes For Pressure Switch Open Fault

Clean Or Clear Venting And Intake

Remove debris, nests, or ice from the flue, chimney, and intake. Ensure proper termination clearances and that the vent pipe is not crushed or sagging. For PVC venting, inspect joints and slopes that could trap condensate. Clearing vents often resolves the pressure switch open error.

Replace Vacuum Hose

Replace brittle or collapsed vacuum tubing with correct-size hose and secure with clamps. Ensure the hose path avoids kinks and places where moisture could collect. A simple hose replacement can restore proper pressure sensing.

Replace The Pressure Switch

If the switch fails continuity testing but pressure conditions are correct, replace the pressure switch with an OEM-equivalent Nordyne part. Confirm electrical ratings and pressure set points match the original to maintain safety performance.

Repair Or Replace Inducer Motor

If the inducer motor runs weakly or intermittently, inspect the motor, capacitor, and mounting. Replace the motor or capacitor to restore proper draft. Tighten mounting fasteners and correct misalignments that could hamper airflow.

Fix Wiring And Control Issues

Repair loose or corroded wiring and terminal connections. If the control board shows abnormal behavior or fails to detect the switch, evaluate board relays and voltage outputs. Replace the control board only after verifying other components are functional, since boards are costlier to replace.

Advanced Diagnostics For Technicians

Technicians should use a digital manometer to compare pressure with OEM charts and check for differential pressure across inducer and venting. Oscilloscope traces of inducer motor current can reveal intermittent electrical problems. Check temperature/pressure limits and draft inducer curves for high-efficiency condensing units where condensate drainage affects pressure readings.

Parts, Cost Estimates, And Replacement Tips

Typical replacement parts and rough U.S. retail price ranges: pressure switch $20–$80, inducer motor $150–$450, vacuum hose $3–$15, control board $200–$600. Labor for a qualified HVAC technician ranges widely; expect $100–$300 for diagnostics plus $75–$150 per hour for repairs depending on region and complexity.

When To Call A Professional

Call a licensed HVAC technician if the homeowner is uncomfortable with gas or electrical systems, if the inducer motor must be replaced, if the control board requires diagnosis, or if repeated pressure switch faults persist after basic troubleshooting. Professionals provide safe gas handling, accurate pressure measurements, and warranty-compliant repairs.

Preventive Maintenance To Avoid Pressure Switch Faults

• Schedule annual HVAC tune-ups to inspect inducer, pressure switch, and venting.
• Keep outdoor vent terminations clear of debris, snow, and ice.
• Inspect vacuum hoses and replace brittle ones during routine service.
• Ensure proper condensate drainage for high-efficiency units to prevent hose or switch contamination.
• Monitor for unusual sounds or repeated lockouts and address promptly.

Troubleshooting Flow Table

Symptom	Initial Check	Next Step
Inducer runs but no ignition	Check hose and switch continuity	Test pressure with manometer; replace switch if pressure present
Inducer weak	Check capacitor and mounting	Replace inducer motor or capacitor
Intermittent open faults	Inspect wiring and moisture in hose	Replace hose, clean vents, test multiple cycles

Common FAQ About Nordyne Pressure Switch Open Fault

Can Power Cycling Clear The Error?

Power cycling may temporarily reset the control board and clear a fault, but it does not fix underlying problems. If the pressure switch open fault returns, follow diagnostic steps to identify the root cause.

Is It Safe To Bypass The Pressure Switch?

Never bypass the pressure switch. It’s a critical safety device that prevents ignition under unsafe venting conditions. Bypassing risks carbon monoxide buildup and is illegal and dangerous.

How Long Does A Pressure Switch Last?

Pressure switches can last many years but may fail sooner due to moisture, corrosion, or mechanical wear. Regular inspections during annual service prolong switch life.

Key Takeaways

Pressure switch open faults are usually caused by venting restrictions, inducer problems, faulty hoses, or a bad switch. Systematic troubleshooting—visual checks, hose and continuity tests, inducer inspection, and pressure measurement—resolves most issues. Prioritize safety and contact a licensed HVAC technician for gas or electrical repairs beyond basic homeowner checks.