Electrical Troubleshooting Flashcards

An aircraft pitot heat circuit draws 8 amps normally but now draws only 2 amps with full voltage applied. This most likely indicates:

Answer: An open or partial open in the heater element increasing resistance

Lower-than-normal current with correct voltage indicates increased resistance, such as a partially open or deteriorated heating element.

When troubleshooting a faulty fuel quantity indicator, a technician should verify the sender resistance by:

Answer: Disconnecting the sender and measuring resistance at the sender connector pins

Disconnecting the sender and measuring its resistance directly verifies whether the sender or indicator is faulty before replacing components.

A transponder fails the ramp test for Mode C altitude encoding. After confirming the transponder is serviceable, the technician should check the:

Answer: Encoding altimeter or blind encoder and associated wiring

Mode C altitude data comes from the encoding altimeter or blind encoder — a wiring or encoder fault will cause incorrect altitude reporting despite a serviceable transponder.

A technician measures 0 ohms between the positive terminal of an aircraft component and aircraft ground with the circuit de-energized. This indicates:

Answer: A direct short circuit to ground in the component or wiring

Zero resistance between a positive circuit terminal and ground (with the circuit de-energized) indicates a direct short to ground that would blow fuses or trip breakers when powered.

When an aircraft static inverter fails, the FIRST check should be:

Answer: Verify DC input voltage and current draw at inverter input terminals

Confirming correct DC input voltage and current establishes whether the inverter is receiving power before diagnosing internal faults.

An aircraft has multiple avionics units failing simultaneously. The technician should first suspect:

Answer: A common power bus, ground, or power supply fault

Simultaneous failure of multiple units sharing a common bus or ground points to a single upstream fault rather than multiple independent component failures.

During a resistance check of an aircraft wiring harness connector, a technician finds 0.8 ohms on a pin that should measure below 0.1 ohms. The BEST corrective action is to:

Answer: Clean or replace the connector to restore proper contact resistance

Connector contact resistance above specification indicates contamination, corrosion, or wear that requires cleaning or connector replacement to prevent voltage drop and heat buildup.