Maintenance & Troubleshooting Techniques Flashcards

What is the correct sequence when using the 'substitution method' for troubleshooting?

Answer: Swap one suspect component at a time with a known-good unit and test after each substitution

Replacing one component at a time and testing after each swap identifies the faulty part without introducing multiple changes that could confuse the diagnosis.

Thermographic imaging during an electrical panel inspection reveals a hot spot on a circuit breaker. The appropriate response is to:

Answer: Investigate for loose connections, overloading, or breaker degradation before the next scheduled PM

Thermal anomalies on breakers indicate resistance heating from loose connections or internal degradation and require prompt investigation to prevent fire or failure.

When a system fails immediately after a component was replaced, the technician should first:

Answer: Verify the replacement part specification, installation orientation, and configuration settings

Post-replacement failures most often trace back to incorrect part specification, reversed installation, or missed configuration steps during the replacement procedure.

In a refrigeration system, high discharge pressure combined with low suction pressure most likely indicates:

Answer: A restriction in the liquid line or a faulty expansion device

A restriction downstream of the condenser (liquid line or expansion device) creates high head pressure and starves the evaporator, dropping suction pressure.

Which maintenance metric directly measures the average time required to restore a failed system to operational status?

Answer: Mean Time To Repair (MTTR)

MTTR measures the average repair duration from failure detection to return-to-service, directly quantifying maintenance team responsiveness and repair efficiency.

A technician finds corrosion inside an electrical junction box. After cleaning and repairing the connections, the long-term corrective action should include:

Answer: Identifying and eliminating the moisture ingress source and upgrading enclosure sealing if needed

Cleaning treats the symptom; eliminating moisture ingress at its source and ensuring the enclosure IP rating matches the environment prevents recurrence.

When a technician suspects electromagnetic interference (EMI) is causing spurious faults in a control system, the most effective diagnostic step is to:

Answer: Identify and document fault timing relative to nearby high-current switching events

Correlating fault timing with nearby switching events (motors starting, contactors operating) confirms EMI as the source before committing to mitigation measures.