Turn signal light bulbs are a common “wear and tear” item in your vehicle electrical system. The bulbs on most vehicles utilize a filament that literally burns up, in the same way that old incandescent household light bulbs would burn out at home. In some cases, a bad connection due to corrosion at the light bulb socket, or a wiring issue to the light bulb, can also cause a “no turn signal” condition. Since turn signals trigger both a front and rear turn bulb, most bulb failure scenarios can be easily diagnosed, although repair may best be left to a professional who will replace the turn signal light bulb. Some of the symptoms of a failed turn signal light bulb include:
1. Turn signal indicator in the instrument cluster comes on solid and does not blink
This is a common failure mode, and can be checked while your vehicle is stationary in your driveway or other safe location. To check to see whether it’s the front or rear turn signal bulb that has failed, walk around the vehicle after selecting a turn signal direction, to see which of the turn lights (for the turn side you selected), front or rear, is not illuminated. For example, a solid turn indicator for a left turn, with the front turn bulb on constantly, but no left rear turn bulb illuminated, indicates that the left rear turn light bulb has failed.
2. Turn signal indicator blinks very fast
This is another common failure mode. To check to see whether it’s the front or rear turn signal light bulb that has failed, walk around the vehicle (stationary and in a safe location of course!) to see which of the turn lights (for the turn side you selected), front or rear, is not illuminated. For example, a rapidly flashing turn indicator for a right turn, with the right front turn bulb blinking rapidly, but no right rear turn bulb, indicates that the right rear turn light bulb has failed.
3. Both turn light bulbs on the left, or both turn light bulbs on the right, do not blink
4. Both right and left turn indicators do not work properly
This symptom may be observed if the hazard warning/turn signal flasher unit, which is integrated, itself has failed. This can be verified by pressing the hazard warning button in your vehicle. CAUTION: Only perform this test off the road in a safe location! If the left AND right turn signal indicator lights do not flash as expected, it is likely the hazard warning and turn signal flasher unit has failed. If the symptoms and diagnosis above indicate that the hazard warning and turn signal flasher unit has failed, a professional mechanic can replace the hazard warning and turn signal flasher unit.
Another possibility for this symptom is that an electrical overload in the turn signal circuitry has caused a fuse to blow, protecting the circuit, but not allowing the turn signals to function. A YourMechanic turn signal inspection will identify if this is the case.