NATE Air Conditioning and Heat Pumps Practice Exam

A small voltage reading across a closed set of contacts in an energized circuit indicates that the ____.

1. Contacts are in good condition

2. Contacts are pitted

3. Motor capacitor is defective

4. Wrong voltage is supplied to the unit

The correct answer is: Contacts are pitted

A small voltage reading across a closed set of contacts in an energized circuit typically suggests that there is an issue with the contacts, particularly that they might be pitted or corroded. When contacts are in good condition, you would expect minimal to no voltage drop across them when they are closed, as they should be allowing current to flow freely without resistance. Pitting occurs when contacts repeatedly open and close under load, leading to material erosion and creating poor contact surfaces. This deteriorates their ability to conduct electricity effectively, resulting in a voltage reading that indicates some resistance or interruption in the current flow despite the contacts being closed. In contrast, if the contacts were in good condition, there should ideally be a negligible voltage across them. Options about a defective motor capacitor or wrong voltage supply pertain to different electrical issues that would not primarily indicate the condition of the contacts.