Automotive Service Excellence (ASE) A6 Electrical/Electronic SystemsLighting Systems Diagnosis and RepairHard
A technician is diagnosing a vehicle where the right front turn signal illuminates steadily but does not flash. The left turn signal operates normally, and the hazard lights flash correctly on both sides. The vehicle uses an electronic flasher relay. What is the MOST likely cause?
- AA defective electronic flasher relay.
- BA faulty right front turn signal bulb.
- CAn open circuit in the ground wire for the right front turn signal.
- DA short circuit in the right front turn signal wiring.
Show answer & explanationAnswer & explanation
Correct answer: A. A defective electronic flasher relay.
Since the right front turn signal illuminates but doesn't flash, and the hazard lights (which use the same flasher) work correctly, it suggests that the flasher relay itself is working for the hazard function, but its internal logic or output for the single turn signal circuit is faulty, causing a steady illumination. This is a specific failure mode for electronic flashers.
Why the other options are wrong
- B. A faulty bulb (open filament) would typically cause hyper-flashing, not steady illumination.
- C. An open ground would prevent the bulb from illuminating at all, not cause steady illumination.
- D. A short circuit would likely blow a fuse or prevent illumination, not cause steady illumination without flashing.
Electronic Flasher Relay Failure Modes
Electronic flasher relays, unlike thermal ones, can have more complex failure modes beyond simply not flashing. They might flash incorrectly, flash only one side, or provide steady power without flashing.
- Uses solid-state components, no moving parts.
- Often integrated into a BCM or dedicated module.
- Failure can manifest as hyper-flashing, no flashing, or steady illumination.
Memory trick: Steady light, flasher's plight!