AGL-CS-054 — Taxiway Light Connector Failure
The AGL Knowledge Hub | Engineering Case Study Series. A taxiway lighting investigation where one taxiway centreline light exhibited intermittent operation due to connector corrosion and thermal damage — from CCR verification through resistance measurement, thermal inspection, connector disassembly, and replacement.
Important: This is an engineering simulation created for training. It is not presented as an actual airport incident. All readings, values, dates and outcomes are illustrative, and no airport, organisation, person or manufacturer is identified or implied.
1Case Study Overview
During routine night inspection, one taxiway centreline light exhibited intermittent operation, while adjacent taxiway lights remained fully operational.
The Constant Current Regulator (CCR) was maintaining the selected 6.6 A current, output voltage was normal, and no CCR alarms were present.
Because the fault was intermittent and localized, the investigation focused on the secondary connector assembly, transformer secondary terminals, and connector contact integrity.
A systematic investigation identified severe corrosion and thermal damage inside the L-823 connector assembly, which caused high contact resistance and intermittent interruption of the transformer secondary circuit.
This case demonstrates that connector failures are one of the most common and often misdiagnosed causes of taxiway light outages and intermittent lighting behavior.
2Learning Objectives
After completing this case study, the learner should be able to:
- Diagnose taxiway light connector failures.
- Understand L-823 connector construction and function.
- Measure connector contact resistance.
- Investigate intermittent secondary-circuit faults.
- Identify moisture-related connector corrosion.
- Assess thermal damage caused by poor electrical contacts.
- Restore connector reliability safely.
3System Background
A taxiway light secondary circuit consists of:
The connector provides:
- Electrical continuity.
- Environmental sealing.
- Mechanical connection.
- Secondary-circuit reliability.
Common connector failure causes include:
- Moisture ingress.
- Corrosion.
- Contact oxidation.
- Improper assembly.
- Mechanical damage.
- Thermal cycling.
- Loose electrical connections.
4Problem Statement
The reported condition was:
- One taxiway light intermittent.
- Adjacent lights normal.
- CCR healthy.
- No circuit alarms.
- Intermittent operation increased during wet weather.
Is the taxiway fixture defective, or is the connector interrupting the secondary power supply?
5Initial Observations
| CCR status | Healthy |
| Selected current | 6.6 A |
| Actual current | 6.6 A |
| Output voltage | Normal |
| Adjacent lights | Operational |
| Failed light | Intermittent |
Intermittent operation strongly suggested a connection-related defect.
6Initial Engineering Hypotheses
The maintenance team considered:
LED module failure.
Transformer secondary failure.
Connector contact corrosion.
Secondary cable conductor break.
Moisture-related connector failure.
7Connector Failure Principle
Normal connector:
Failed connector:
Connector failures often become temperature-dependent and moisture-dependent.
8Test Equipment
The investigation used:
- True-RMS multimeter.
- Low-resistance ohmmeter.
- Thermal imaging camera.
- Secondary voltage test equipment.
- Insulation resistance tester.
- Moisture inspection equipment.
- Approved AGL circuit test equipment.
- Airport-approved PPE.
9Investigation
Step 1: Verify CCR Operation
Results:
| Current regulation | Normal |
| Voltage regulation | Normal |
| CCR alarms | None |
The CCR was healthy.
Step 2: Verify Transformer Primary
The associated transformer showed:
- Primary current present.
- Normal operating temperature.
- Stable operation.
Primary power was available.
Step 3: Measure Transformer Secondary Voltage
Results:
| Connector connected | Intermittent voltage |
| Connector disconnected | Stable transformer output |
The transformer was healthy.
Step 4: Connector Resistance Measurement
Measured connector resistance:
0.85 Ω
Expected value:
Less than 0.05 Ω
The connector resistance was abnormally high.
Step 5: Thermal Inspection
Thermal imaging showed:
- Connector temperature significantly higher than adjacent connectors.
- Localized heating at one contact.
- Temperature increase during operation.
The connector was generating heat because of contact resistance.
Step 6: Connector Disassembly
Inspection revealed:
- Moisture contamination.
- Green copper corrosion.
- Oxidized contact surfaces.
- Carbonized contact area.
- Reduced contact pressure.
- Deteriorated sealing components.
The connector had failed both electrically and mechanically.
Step 7: Secondary Cable Verification
The secondary cable showed:
- Normal continuity.
- Normal insulation resistance.
- No conductor damage.
The connector was confirmed as the primary failure point.
10Root Cause
The taxiway light connector failure was caused by moisture ingress into the L-823 connector assembly, resulting in corrosion of the contact surfaces and increased contact resistance.
The elevated contact resistance produced:
- Voltage drop.
- Localized heating.
- Thermal deterioration.
- Intermittent secondary-circuit interruption.
- Taxiway light outage.
The transformer and fixture remained healthy.
11Corrective Action
The maintenance team:
- Isolated the circuit.
- Removed the damaged connector.
- Cleaned the transformer secondary terminals.
- Installed a new approved L-823 connector.
- Restored proper sealing.
- Verified contact resistance.
- Measured secondary voltage.
- Performed thermal verification.
- Tested taxiway light operation.
- Updated maintenance records.
12Post-Repair Verification
The taxiway light operated normally after connector replacement.
13Root-Cause Analysis
Taxiway light intermittent
Healthy
Healthy
Intermittent
High
Corrosion identified
Moisture-induced connector contact deterioration
Replace connector and restore sealing
14Why This Case Was Important
Connector failures can produce:
- Intermittent lights.
- Dim lights.
- Thermal damage.
- Transformer overheating.
- Repeated fixture replacement.
- Difficult troubleshooting.
Connector resistance should always be considered before replacing major components.
15Engineering Lessons
Intermittent operation often indicates connector problems.
Intermittent operation often indicates connector problems.
Contact resistance measurement is a powerful diagnostic tool.
Contact resistance measurement is a powerful diagnostic tool.
Thermal imaging can quickly identify failing connectors.
Thermal imaging can quickly identify failing connectors.
Moisture ingress accelerates connector corrosion.
Moisture ingress accelerates connector corrosion.
Proper connector sealing is critical for taxiway lighting reliability.
Proper connector sealing is critical for taxiway lighting reliability.
16Engineer's Decision Point
You observe: One taxiway light intermittent. CCR healthy. Transformer healthy. Connector warm during operation. What should you investigate first?
17Knowledge Check
18Interview Questions
19Frequently Asked Questions
Quick answers about taxiway light connector failure, based on this case study.
Q1What is AGL-CS-054?
AGL-CS-054 is an engineering training case study on an intermittently operating taxiway centreline light traced to an L-823 connector failure. It is an engineering simulation created for training, not a report of an actual airport incident.
Q2Why did the light work only intermittently?
Moisture had corroded the connector contacts and raised contact resistance, producing voltage drop, localized heating and intermittent interruption of the secondary circuit. The intermittent operation increased during wet weather.
Q3What was the root cause?
Moisture ingress into the L-823 connector assembly caused corrosion of the contact surfaces and increased contact resistance, with severe corrosion and thermal damage found inside the connector. The transformer and fixture remained healthy.
Q4What should you investigate first?
Measure connector contact resistance and inspect the connector assembly for corrosion, sealing failure and thermal damage. Replacing the CCR, transformer or fixture is not the right first step.
Q5Which test equipment was used?
The team used a true-RMS multimeter, low-resistance ohmmeter, thermal imaging camera, secondary voltage test equipment, insulation resistance tester and moisture inspection equipment.
Q6How was the light repaired?
The team isolated the circuit, removed the damaged connector and cleaned the transformer secondary terminals. They installed a new approved L-823 connector, restored proper sealing, verified contact resistance, measured secondary voltage, performed thermal verification and tested the light.
Q7How was the repair verified?
Connector resistance was less than 0.05 Ω, secondary voltage and light operation were stable and connector temperature was normal.
Q8How does a warm connector help diagnose the fault?
In the decision-point scenario, a connector that is warm during operation while the CCR and transformer are healthy points to a connector problem. Thermal imaging can show this before a full failure.
Engineering & Expert Notes
Check Connector Compatibility and Condition Together
ConnectorsA worn or mismatched connector can mimic corrosion. Inspect both mating halves.
Compare Temperatures Under Load
ThermographyA warm connector against its neighbours signals contact resistance. Record conditions with each image.
Controlled Movement Tests Only Under Isolation
TechniqueIf intermittent, movement tests may expose it, but only with isolation and permits in place.
Renew Seals Whenever the Connector Is Re-Made
SealingWithout a fresh seal the same moisture path returns.
20Case Study Conclusion
Taxiway light connector failure is primarily a secondary-circuit contact deterioration problem caused by moisture ingress, corrosion, and increased contact resistance, leading to voltage drop, thermal heating, intermittent operation, and eventual circuit interruption.
Systematic CCR verification, transformer testing, contact-resistance measurement, thermal inspection, connector examination, and sealing verification can rapidly identify connector failures and restore reliable taxiway lighting operation.
In AGL engineering, the connector is often the smallest component in the circuit, but it can create the largest reliability problem on the taxiway.
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