Key Takeaway
You can tell a pressure switch is not working if your system behaves oddly — like a pump that never starts or never stops, even when pressure changes. Another sign is if the system runs constantly or shuts off too early. Sometimes, you won’t hear the usual “click” when pressure rises or falls. This means the switch isn’t activating. You can also check with a pressure gauge and see if pressure goes past the switch setting without triggering it. For electrical switches, use a multimeter to check if the contacts are switching properly. Dirt, rust, or mechanical wear inside the switch can block its function. If you notice leaking, burnt wires, or broken springs, those are signs of failure too. A faulty pressure switch can waste energy, damage equipment, or lead to unsafe pressure. When in doubt, test it properly or replace it to avoid further problems.
No Pressure-Based Activation in the System
If a system isn’t activating based on pressure, the pressure switch could be the problem. Possible causes include incorrect setpoints, worn-out internal components, damaged wiring, or improper installation. Sometimes, the system pressure never actually reaches the cut-in point due to leaks, blockages, or a weak pump. Visually inspect the switch and test with a multimeter and pressure gauge to confirm activation. If the switch doesn’t respond, try adjusting the setpoint or replacing it. A non-responsive switch can lead to equipment shutdown, poor performance, or safety hazards. Diagnosing the issue early prevents downtime and ensures the system operates smoothly under varying pressure conditions.
Intermittent or Erratic Start/Stop Behavior
Let’s say your system starts today, then randomly shuts down tomorrow. No pattern. No warning. Just erratic behavior. That’s your pressure switch waving a red flag.
When a pressure switch is faulty—but not completely dead—it behaves like a moody teenager. Sometimes it obeys. Sometimes it doesn’t. And that inconsistency is dangerous, especially in critical applications like compressors, booster pumps, or HVAC systems.
Imagine a factory water system that suddenly shuts off midway through production. The loss of pressure triggers alarms. Downtime begins. All because the pressure switch contact might be oxidized or bouncing.
Here’s how to verify it: Use a multimeter and watch how the readings jump when the system pressure hits the setpoint. If the switch opens/closes erratically, or flickers on your test device, that’s your sign.
System Stays Off Despite Sufficient Pressure
Now picture this: the gauge reads 4 bar, but your compressor doesn’t restart. It’s quiet. Too quiet. And you know something’s off.
This is a classic case where the system stays off—even when it shouldn’t. This is usually because the pressure switch is stuck in the “open” position. It fails to sense that the pressure has dropped below the setpoint, or it fails to close the contact circuit needed to power up the machine.
This kind of failure is deceptive. To a fresh engineer, it may seem like a power issue. But seasoned technicians know better. It’s the switch.
The internal spring mechanism might be jammed. Or the diaphragm may have stiffened over time. Especially in older switches or systems exposed to high temperatures or chemical vapors, components inside the switch degrade.
And if you’re working with a digital switch? A faulty sensor or corroded circuit board might be to blame. Either way, the command doesn’t go through.
Visual Damage or Corrosion on Terminals
Sometimes, all it takes is one look.
If you open the panel and spot greenish rust, burnt marks, or brittle wires around the pressure switch, it’s a clear sign of trouble. In fact, 80% of the time, visible corrosion on terminals is the root cause of malfunction.
Corroded terminals mean poor electrical contact. That leads to increased resistance, heat generation, and ultimately, switch failure. If left unchecked, it could damage connected equipment too.
Take a torch and inspect the terminals closely. Is the screw loose? Are the connectors oxidized? If yes, clean the contacts with a soft brush or terminal cleaner. But if the damage is deep, replacing the switch is the safer option.
In humid environments or outdoor applications, always use sealed or IP-rated switches. Moisture and dust are silent killers. Even inside panels, condensation can settle overnight and corrode terminals.
We once had a case where the pressure switch in a dairy plant kept failing. Turned out it was placed near a vent pipe that released steam twice a day. That moisture killed three switches in one quarter—until we fixed the location and used sealed units.
Water or Oil Leakage Near the Switch
Leaks are not just messy—they’re dangerous.
If you notice oil or water dripping near or from your pressure switch, stop the system. This means the diaphragm is torn, or the enclosure is compromised.
Why does it matter? Because pressure switches are supposed to isolate the fluid from the electrical components. The moment that barrier is breached, you risk short circuits, equipment damage, or even fire in worst-case scenarios.
Sometimes, leaks may not be dramatic. A small ring of moisture, or a slow oil stain on the switch base, is enough to indicate internal damage.
In pneumatic systems, oil leaks can result from over-lubricated air lines. In hydraulic systems, it could mean the pressure switch seal has given way.
Check the mounting threads too. If the switch wasn’t properly tightened, or if Teflon tape was used poorly, leaks will occur.
Always shut down and isolate the system before attempting any repairs. Don’t just wipe and move on. Take the time to replace the faulty switch.
Conclusion
Pressure switch failure rarely happens without warning. If you notice irregular system behavior—such as pumps not turning on, frequent short cycling, or no response at expected pressure points—it may be time for a switch inspection. Visual clues like burnt contacts, moisture near terminals, or physical cracks also signal trouble. Another sign is inconsistent cut-in or cut-out pressure, where the system operates out of sync with the switch settings. Sudden surges or pressure build-up with no switching response can be dangerous and costly. If your system stays off even with correct pressure, or stays on longer than usual, the internal mechanism may be worn or stuck. Regular inspections help detect these problems early. Ignoring them can lead to overheating, equipment wear, or complete system shutdown. Don’t wait for a breakdown. Spotting the early signs of failure helps avoid downtime, protects your equipment, and keeps operations running safely and efficiently.