Solennoids are the workhorses of countless industrial and consumer applications—from medical devices and automotive systems to agricultural drones and pet training collars. But like any electromechanical component, they can and do fail. Understanding why solenoids fail is the first step to preventing downtime, reducing warranty claims, and extending product life.

This guide covers the most common solenoid failure modes—including overheating, coil burnout, shorting, mechanical jamming, and insufficient force testing—and provides actionable prevention strategies.

1. Overheating & Coil Burnout (The #1 Cause)

Overheating is by far the most common cause of solenoid failure . When a solenoid coil exceeds its maximum temperature rating, the enamel insulation on the copper wire breaks down, causing shorts between turns, reduced resistance, increased current, and a thermal runaway effect that ends in burnout .

Why Overheating Happens

• Plunger fails to close: When energized, a solenoid draws a high inrush current that drops once the plunger seats. If the plunger is blocked or jammed, the high current continues, rapidly overheating the coil .
• Excessive duty cycle: Running a solenoid beyond its rated duty cycle (e.g., 100% continuous when rated for 10%) prevents adequate cooling between cycles .
• High ambient temperature: Heat dissipation is reduced in hot environments, causing the coil to reach critical temperatures even under normal operation .
• Overvoltage: While less common, applying a higher voltage than rated increases holding current and gradually overheats the coil .
• Energizing without a plunger: Running a solenoid without its magnetic plunger draws higher-than-intended current .

How to Prevent Overheating

• Verify duty cycle ratings – Choose a solenoid with a duty cycle that matches your actual ON/OFF timing. If you need continuous operation, specify a continuous-duty solenoid or a larger frame size for better heat dissipation .
• Check plunger movement – Ensure the plunger moves freely and seats completely. Debris, corrosion, or misalignment can prevent full closure .
• Consider insulation class – For high-temperature environments, specify Class F (155°C) or Class H (180°C) insulation instead of standard Class A (105°C) .
• Add thermal protection – Some solenoids include thermal fuses or cutoffs that disconnect power when temperature exceeds a safe threshold .
• Monitor supply voltage – A voltage drop can reduce force and prevent full closure; overvoltage causes excess heat. Maintain stable voltage within ±5% of rated .

2. Mechanical Jamming & Blocked Plunger

A solenoid that fails after only a few hundred cycles—or stops working entirely—often has a mechanical issue. The plunger may be physically blocked, preventing it from completing its stroke .

Common Causes

• Debris ingress: Dust, dirt, sand, or metallic particles can accumulate in the air gap or along the plunger bore, causing friction or complete jamming .
• Corrosion: Moisture, chemicals, or even salt vapor can corrode the plunger or bore, increasing friction or causing sticking .
• Misalignment: Side loads from improper mounting or linkage can bind the plunger, preventing full stroke .
• Residual magnetism: In rare cases, residual magnetism can cause the plunger to stick in the energized position even after power is removed .

Prevention Strategies

• Specify IP-rated enclosures – For dusty or wet environments, use sealed solenoids with appropriate Ingress Protection (IP) ratings .
• Use corrosion-resistant materials – Stainless steel plungers or protective platings (nickel, zinc) resist corrosion in harsh environments .
• Ensure straight-line actuation – Design your mechanism to apply force along the plunger axis, avoiding side loads that cause binding .
• Inspect and clean – Regular maintenance to remove debris from the solenoid bore can prevent jamming.

3. Shorting & Insulation Failure

Electrical shorts can occur between coil windings (turn-to-turn shorts) or between the coil and the solenoid housing (ground shorts). These are often precursors to complete burnout .

Causes of Shorting

• Moisture ingress: Water-based coolants or condensation can carry conductive particles into lead wire junctions, creating short circuits .
• Insulation breakdown: Overheating degrades enamel insulation, allowing adjacent turns to touch .
• Mechanical damage: Abrasion or crushing of lead wires during installation can expose conductors.

Prevention

• Use encapsulated coils – Potting or molding the coil in epoxy or plastic protects against moisture and physical damage.
• Protect lead wire junctions – Use heat-shrink tubing or sealed connectors to prevent moisture ingress at connection points.
• Avoid over-torquing – When mounting, do not crush or pinch coil leads.

4. Missing Load Testing (Force Verification)

A solenoid that works on the bench but fails in the field often hasn't been properly tested against its actual operating load. Force testing is critical because solenoid force varies with stroke, voltage, and temperature .

Why This Matters

• Force drops with stroke: Solenoids produce the most force at the end of stroke and the least at the beginning. If your load requires high initial force, you may need a different design .
• Temperature affects force: As coils heat up, resistance increases, current decreases, and force drops. A solenoid that works at room temperature may fail at operating temperature .
• Weight vs. spring loads: Testing with dead weights gives lower force readings than spring loads because weights have inertia that must be overcome .

Best Practices for Force Testing

• Test at actual operating conditions – Use the same voltage, temperature, and stroke as the final application .
• Measure force at multiple stroke positions – Obtain a force-stroke curve to ensure adequate force throughout the full range of motion .
• Test with a representative load – Use a spring or air cylinder that simulates the actual load characteristics .
• Account for voltage tolerance – If your power supply can drop to 85% of nominal voltage, specify a solenoid that can still move the load at that lower voltage .

5. Solenoid Troubleshooting Checklist

Use this quick checklist when a solenoid fails :

6. How to Prevent Failures During Design

The best way to avoid solenoid failures is to specify correctly from the start. Here's what to provide to your solenoid manufacturer :

• Voltage range – nominal voltage and acceptable tolerance (e.g., 12V DC ±10%)
• Required force at initial and end stroke – in Newtons (N) or grams
• Stroke length – the exact travel distance required
• Duty cycle – ON time vs. total cycle time
• Ambient temperature range – minimum and maximum expected
• Environmental factors – dust, moisture, chemicals, vibration
• Cycle life requirement – expected number of operations

7. Conclusion

Most solenoid failures are preventable. By understanding the failure mechanisms—overheating, mechanical jamming, shorting, and missed load testing—you can make better design choices, specify appropriate materials and ratings, and implement effective testing procedures.

When in doubt, work with a custom solenoid manufacturer like NEXTCORE ELECTRONIC that understands your application, provides force-stroke testing, and offers sample validation before mass production.

FAQ – Common Solenoid Questions