When troubleshooting a 120 V AC control circuit, a technician measures 120 V AC at the 'HOT' side of a normally open (NO) push button, but 0 V AC at the 'LOAD' side when the button is pressed. What is the most probable issue with the push button?

Question: When troubleshooting a 120 V AC control circuit, a technician measures 120 V AC at the 'HOT' side of a normally open (NO) push button, but 0 V AC at the 'LOAD' side when the button is pressed. What is the most probable issue with the push button?

Answer options:

• The push button has an internal short circuit.
• The push button is miswired as normally closed (NC). ✅ The contacts of the push button are dirty or oxidized.
• The push button's spring mechanism is faulty.

Correct answer: The contacts of the push button are dirty or oxidized.

Explanation: If 120 V is present on one side when pressed, but 0 V on the other, it indicates an open circuit within the push button's contacts, preventing current flow. Dirty or oxidized contacts are a common cause of high resistance or open circuits, especially in industrial environments. A short circuit would result in a fuse or breaker trip, and miswiring would show voltage differently, while a faulty spring affects physical action, not electrical continuity within the contacts.