What causes plunger switches to stick?

• A. Dust, dirt and paint
• B. Excessive lubrication
• C. High humidity
• D. Magnetic interference

Answer: (B)

Excessive lubrication causes plunger switches to stick because the excess lubricant leaves a thick, viscous film inside the switch. This film can trap dust, debris, and paint specks and create friction between the plunger and its bore, so the plunger can no longer move freely and may stay in a pressed or released position. The switch is designed to operate with minimal or no lubrication, so over-lubrication disrupts its smooth movement. Magnetic interference isn’t a factor for these mechanical plunger switches, and humidity or dirt alone can cause problems, but the primary maintenance-related cause of sticking is too much lubricant. If a switch sticks, cleaning and ensuring only a light, appropriate lubrication (or none, per manufacturer guidance) is usually the fix.