* Turn Signal Switch: This is the most common culprit. The switch controls the left and right turn signals individually, while the hazard lights use a separate circuit that bypasses the switch. A faulty switch can fail to send power to the appropriate side's turn signal lamps but still allow the hazards to function, which use a different portion of the switch.
* Wiring Issues: A break or short in the wiring for the left or right turn signal circuits is possible. This could be anywhere between the switch, the flasher relay, and the lights themselves. A rodent chew, damaged harness, or corroded connection is a likely suspect. Check the wiring harnesses carefully, especially near the steering column and the taillights.
* Turn Signal Flasher Relay: While less likely given the hazards work, a faulty flasher relay *could* cause this issue. The relay controls the flashing action. If it's failing intermittently or only affecting the turn signals, it's a possibility.
* Bulbs: Burned-out bulbs are unlikely to be the sole cause if the hazards are working (hazards use the same bulbs as turn signals), but check them anyway. A blown bulb can sometimes disrupt the circuit enough to prevent the flasher from working correctly.
* Multi-function switch (turn signal stalk): This is essentially the same as the turn signal switch but sometimes the term "multi-function switch" is used for the whole assembly.
* Grounding Issues: A poor ground connection can prevent the signals from working correctly.
Troubleshooting Steps:
1. Check the Bulbs: This is the easiest first step. Replace any burned-out bulbs in the front and rear turn signal assemblies.
2. Inspect the Fuses: Check the fuses related to the turn signals in the fuse box. Consult your owner's manual to locate the correct fuses.
3. Test the Flasher Relay: If you have a spare flasher relay, swap it out to see if that resolves the issue.
4. Wiring Inspection: This is the most involved step and often requires some electrical knowledge. Carefully inspect the wiring harnesses for any visible damage, breaks, or corrosion. A multimeter can help you trace the circuits and check for continuity.
5. Turn Signal Switch Testing: This is best done by a mechanic with the appropriate testing tools and knowledge. It requires access to the switch, and often means removing the steering column cover.
If you're not comfortable working with car electrical systems, it's best to take your Monte Carlo to a qualified mechanic for diagnosis and repair. The problem could be relatively simple (a blown bulb), or it could require more advanced troubleshooting and component replacement.
