ASE G1 Auto Maintenance and Light RepairElectrical/Electronic SystemsMedium
A vehicle's left turn signal blinks rapidly, while the right turn signal blinks at a normal rate. All bulbs on the left side (front and rear) are confirmed to be illuminating. What is the MOST likely cause?
- AA short circuit in the left turn signal wiring.
- BA faulty flasher unit.
- CA poor ground connection for one of the left turn signal bulbs.
- DIncorrect wattage bulb installed on the left side.
Show answer & explanationAnswer & explanation
Correct answer: D. Incorrect wattage bulb installed on the left side.
A rapid turn signal blink rate (hyper-flashing) typically indicates that the flasher unit detects a lower-than-normal current draw, which it interprets as a burned-out bulb. If all bulbs are illuminating, the most common reason for lower current draw with working bulbs is the installation of an incorrect wattage bulb (e.g., an LED bulb without a resistor, or a lower-wattage incandescent bulb) that draws less current than the system expects.
Why the other options are wrong
- A. A short circuit would cause excessive current draw, likely blowing a fuse, not causing rapid blinking with all bulbs working.
- B. A faulty flasher unit would typically affect both turn signals, or cause no flashing at all, not just one side. Modern flashers are often integrated into the BCM.
- C. A poor ground connection for a bulb would typically cause it to be dim, not illuminate at all, or cause other erratic behavior, but not necessarily rapid flashing if the other bulb on that side is working fine and the flasher is still detecting some load.
Hyper-Flashing Turn Signals
Rapid blinking of turn signals, usually indicating a bulb outage or incorrect bulb wattage/type.
- Flasher units detect resistance/current draw to determine bulb status.
- Lower-than-expected current draw (e.g., from an LED or lower-wattage bulb) causes hyper-flashing.
- Higher-than-expected current draw (e.g., from a short) typically blows a fuse.
Memory trick: Fast blink, wrong bulb, think.