LLC Troubleshooting & Diagnostics 2 — Questions and Answers
Question 1: A low-voltage landscape lighting system has several fixtures that flicker intermittently. What is the most likely cause?
- Overloaded transformer
- Loose wire connections at the fixture or splice (Correct answer)
- Incorrect lamp wattage
- Transformer timer malfunction
Correct answer: Loose wire connections at the fixture or splice
Loose wire connections cause intermittent contact, resulting in flickering rather than a complete outage.
Question 2: When using a clamp meter to measure current on a low-voltage cable, the reading is 0 amps even though the transformer is energized. What should you check first?
- Replace the clamp meter batteries
- Confirm the clamp is around only one conductor, not both (Correct answer)
- Increase transformer voltage tap
- Test each fixture individually
Correct answer: Confirm the clamp is around only one conductor, not both
Clamping around both conductors causes the opposing currents to cancel, producing a false zero reading.
Question 3: A transformer's GFI (GFCI) outlet keeps tripping whenever a specific lighting zone is activated. What does this most likely indicate?
- The zone has too few fixtures
- There is a ground fault or current leakage on that zone's wiring or fixtures (Correct answer)
- The GFCI outlet needs replacement immediately
- The transformer's voltage tap is too high
Correct answer: There is a ground fault or current leakage on that zone's wiring or fixtures
A GFCI trips when it detects current leaking to ground, indicating a fault in the zone's wiring or a compromised fixture.
Question 4: After a heavy rain, multiple LED path lights in a low-spot zone stop working. The most probable cause is:
- Water infiltration causing a short circuit in the fixtures or connectors (Correct answer)
- Transformer overload from moisture increasing resistance
- Rain-induced voltage spike on the secondary circuit
- Timer drift caused by humidity in the transformer
Correct answer: Water infiltration causing a short circuit in the fixtures or connectors
Water entry into non-watertight fixtures or connectors creates short circuits that cut power to the zone.
Question 5: A technician measures 11.8 VAC at the transformer terminal but only 9.5 VAC at the end of a long cable run. What adjustment should be made?
- Add more fixtures to balance the load
- Switch to a higher voltage tap on the transformer
- Replace the cable with a lower-gauge (thicker) wire or shorten runs (Correct answer)
- Install a secondary transformer at the midpoint
Correct answer: Replace the cable with a lower-gauge (thicker) wire or shorten runs
Voltage drop over long runs is reduced by using heavier-gauge wire or splitting the run, bringing end-of-run voltage into the acceptable range.
Question 6: A path light fixture has a green corrosion buildup on its socket contacts. The BEST corrective action is to:
- Apply a thicker coating of dielectric grease over the corrosion
- Clean contacts with a wire brush or contact cleaner and apply fresh dielectric grease (Correct answer)
- Replace only the lamp and monitor for recurrence
- Increase the wattage of the replacement lamp to burn off corrosion
Correct answer: Clean contacts with a wire brush or contact cleaner and apply fresh dielectric grease
Cleaning corrosion restores proper electrical contact; dielectric grease then protects against future oxidation.
Question 7: A landscape lighting zone runs at the correct voltage but produces noticeably dimmer output than when first installed two years ago. The most likely explanation is:
- The transformer has reduced its output over time
- Lamp lumen depreciation and/or lens clouding on fixtures (Correct answer)
- Soil resistance has increased, loading the circuit
- The timer is restricting full voltage delivery
Correct answer: Lamp lumen depreciation and/or lens clouding on fixtures
Lamp lumen depreciation is normal over time, and UV-clouded lenses reduce light output without causing voltage changes.
LLC Troubleshooting & Diagnostics 2
A low-voltage landscape lighting system has several fixtures that flicker intermittently.
What is the most likely cause?