Cartridge heater failure is most often caused by improper installation, such as a loose fit that prevents proper heat dissipation, or contamination from moisture or impurities which can cause a short circuit. Other common causes include applying incorrect voltage or high watt density, and frequent temperature cycling, which leads to overheating and premature failure of the heating element.

• Loose fit: The most common cause of failure is a loose fit in the bore hole, which creates air gaps and prevents efficient heat transfer.
• Over-tightening: Installing the heater with excessive force can cause mechanical damage.
• Dry-firing: Operating the heater without proper contact with a material to conduct heat can cause it to overheat.

• Moisture and impurities: The hygroscopic nature of the magnesium oxide inside the heater means it can draw in moisture, oils, or other contaminants from the surrounding air, leading to short circuits.
• Corrosion: The heater's materials can degrade over time in corrosive environments, leading to leaks or shorts.

• Incorrect voltage: Applying too high a voltage can drastically increase watt density and cause the heater to fail prematurely.
• High watt density: A watt density that is too high for the application can cause overheating if the heat cannot be dissipated effectively.
• Electrical surges: Power fluctuations or surges can damage the heater's insulation and lifespan.

• Frequent temperature cycling: Rapid on/off cycles can cause the heating element to expand and contract, leading to fatigue and eventual failure.
• Excessive movement: If the heater is mounted to a vibrating or moving machine, it can be susceptible to damage from excess movement.

• Age and usage: Like any component, cartridge heaters have a limited lifespan, and frequent use will cause performance degradation over time.
• Manufacturing defects: Though rare, poor soldering, incorrect winding, or other quality control issues during manufacturing can lead to premature failure.