When troubleshooting a DC indicator that fails to illuminate, which component should you verify first?

When troubleshooting a DC indicator that fails to illuminate, which component should you verify first?

• A. Power supply
• B. Landing gear
• C. Air conditioning
• D. Cabin lights

Answer: (A)

When a DC indicator won’t light, the most important thing to check first is that it’s actually getting power. Indicators rely on a proper power supply to illuminate, so confirming the power path is the quickest way to isolate the fault. Start by verifying the power source to that indicator: confirm the circuit is energized, inspect any fuses or circuit breakers in that loop, and measure the voltage at the indicator’s input. If voltage is present, examine the wiring for loose connections, damage, or corrosion and ensure correct polarity if applicable. If the power is reaching the indicator but it still doesn’t light, the fault is likely in the indicator itself, its bulb or LED, or the control circuit that drives it. If no power is present, repair the power path and the indicator should illuminate once the supply is restored. These other systems (landing gear, air conditioning, cabin lights) are separate loads and don’t directly address why a DC indicator wouldn’t illuminate, so confirming the power supply to the indicator is the logical first step.

When a DC indicator won’t light, the most important thing to check first is that it’s actually getting power. Indicators rely on a proper power supply to illuminate, so confirming the power path is the quickest way to isolate the fault.

Start by verifying the power source to that indicator: confirm the circuit is energized, inspect any fuses or circuit breakers in that loop, and measure the voltage at the indicator’s input. If voltage is present, examine the wiring for loose connections, damage, or corrosion and ensure correct polarity if applicable.

If the power is reaching the indicator but it still doesn’t light, the fault is likely in the indicator itself, its bulb or LED, or the control circuit that drives it. If no power is present, repair the power path and the indicator should illuminate once the supply is restored.

These other systems (landing gear, air conditioning, cabin lights) are separate loads and don’t directly address why a DC indicator wouldn’t illuminate, so confirming the power supply to the indicator is the logical first step.