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airflow Issue

Pressure Switch Problems

Pressure switches verify safe airflow. When they fail, your booth may not start or may give false alarms.

Emergency: (877) 489-3727Start Diagnosis

What You're Experiencing

Pressure or airflow proving switches in the paint booth are malfunctioning, causing operational problems or nuisance alarms.

Visual Signs:

  • Airflow fault on control panel
  • Booth won't start even with fans running
  • Intermittent airflow alarms
  • Pressure switch visibly damaged
  • Tubing disconnected or kinked
  • Manometer reading normal but switch faulted

Sound Signs:

  • Fans running but interlock not satisfied
  • Alarm buzzer for airflow fault
  • No relay click from pressure switch

Safety Risks — Read Before Proceeding

critical(NFPA 33 Section 7.5)

Bypassing airflow verification

Action: Never bypass pressure switches. They verify safe airflow exists before allowing spraying.

high

Operating without adequate airflow

Action: If switch is failed but bypassed, booth may operate with unsafe vapor levels.

medium

Nuisance shutdowns

Action: Intermittent failures cause production interruptions and frustration.

Immediate Steps to Take

  1. 1

    Check sensing tube connections at switch and sensing ports

  2. 2

    Verify tubing is not kinked or clogged

  3. 3

    Check manometer to confirm actual pressure/airflow

  4. 4

    Look for visible switch damage

  5. 5

    Test switch operation with gentle pressure on tube (if safe)

  6. 6

    Check wiring connections to switch

  7. 7

    Note if problem is constant or intermittent

Common Causes

Here are the most likely reasons you're experiencing this problem, ranked by how often we see them.

Sensing Tube Problems

common

Tubing connecting the switch to sensing ports is disconnected, kinked, clogged, or damaged.

Switch Calibration Drift

common

The pressure switch setpoint has drifted from original calibration.

Switch Diaphragm Failure

occasional

Internal diaphragm has ruptured or stiffened, preventing accurate pressure sensing.

Electrical Contact Failure

occasional

Switch contacts are pitted, corroded, or welded, preventing proper switching.

Vibration Damage

occasional

Excessive vibration has damaged the switch or loosened connections.

Actual Airflow Problem

occasional

The switch is working correctly and there really is insufficient airflow.

Interactive Diagnostic Tool

Pressure Switch Diagnostic

Step 1 of 5

Is the sensing tubing properly connected and intact?

If unsafe at any point: If airflow safety cannot be verified, do not spray. Call WERCS at (877) 489-3727.

When to Call WERCS

While some issues can be resolved with basic troubleshooting, these situations require professional service:

  • Switch needs replacement
  • Calibration has drifted
  • Cannot identify problem
  • Multiple switches failing
  • Need system evaluation
  • Chronic nuisance alarms

Priority Service Available

(877) 489-3727

Expert technicians nationwide

Pressure Switch Problems FAQ

Common questions about this issue

Pressure switches (or airflow proving switches) verify that adequate ventilation exists before allowing spraying. They measure the differential pressure created by airflow across filters or in ducts. If airflow is too low, they prevent booth operation—a critical safety function.
Some pressure switches have adjustable setpoints. However, changing the setpoint requires understanding the system design. Setting it too low may allow unsafe operation; too high causes nuisance trips. Have a professional verify proper setpoint.
New filters create less resistance than loaded filters. If the switch senses pressure difference across filters, new filters may not create enough differential to satisfy the switch. This is a calibration or system design issue that needs professional attention.
Include pressure switch testing in monthly inspections. Test by intentionally reducing airflow (blocking a filter briefly) and verifying the switch trips. Annual calibration verification is recommended. Replace switches that don't operate reliably.

Have a question not answered here?

Call us at (877) 489-3727

Related Problems

Airflow AlarmInterlock FaultBooth Not StartingAir Balance Issues

Related Parts & Components

Airflow SensorManometerControl Panel

Can't Fix It? We Can.

WERCS expert technicians service paint booths and extraction systems nationwide. 24/7 emergency service available.

Call (877) 489-3727Request Service Quote