The most common signs of a failing alternator on a G35 are a dying battery while the engine runs, dim or flickering lights and dashboard indicators, and starting or driving problems caused by insufficient electrical power.
In the Infiniti G35, the alternator recharges the battery and powers the car’s electrical systems while the engine runs. When it starts to fail, you may notice a progression from minor electrical quirks to more serious drivability issues. The following signs cover the most typical symptoms and what they mean for your charging system.
Electrical symptoms to watch for
Before listing the specific signs, it helps to understand that the alternator supports nearly every electrical component in the car. If that support wanes, you’ll see a cluster of indicators rather than a single issue.
- Dim or flickering headlights and taillights, especially at idle or during acceleration.
- Battery/charging system warning light illuminated on the dashboard.
- Electrical accessories (power windows, radio, HVAC, instrument cluster) behaving erratically or operating at reduced performance.
- Engine may stall or have trouble starting due to insufficient charging of the electrical system.
- Unusual voltage readings: battery voltage around 12.6V when off, and 13.8–14.8V with the engine running; readings outside this range can indicate charging problems.
- Strange noises from the engine bay near the alternator area (whining, groaning, or squealing belts).
- Burning smell or signs of overheating around the alternator or wiring.
If you notice several of these electrical symptoms at once, the charging system is likely not keeping up and should be tested promptly to prevent a breakdown.
Starting and performance symptoms
Alongside electrical quirks, a failing alternator can manifest as trouble with starting the car or keeping it running smoothly, since the alternator is the primary source of ongoing electrical power after start-up.
- Hard or inconsistent engine cranking, or a vehicle that won’t start despite a fresh battery.
- Engine stalls or dies while driving, particularly when electrical loads are high (AC, lights, etc.).
- Rough idle or misfiring caused by intermittent electrical supply to the engine control module.
- Noticeable drop in performance of electrical systems just as engine load increases (e.g., when turning on headlights or AC).
These signs can overlap with battery or starter issues, so a proper test of the charging system is essential to confirm an alternator problem.
Diagnosis and next steps
If you suspect a bad alternator, start with basic checks and then move to a formal test to confirm the diagnosis. Safety and accurate readings are key to avoid unnecessary repairs.
- With the engine off, measure battery voltage to confirm a healthy battery (about 12.6V). Start the engine and measure again; a healthy alternator typically maintains 13.8–14.8V while running.
- Inspect the drive belt for wear, cracks, looseness, or slipping, as belt issues can mimic alternator failure.
- Check battery terminals and grounds for corrosion, looseness, or damage, and clean or tighten as needed.
- Have a charging-system test performed at a reputable shop or auto parts store. They can measure alternator output under load and verify the voltage regulator function.
Conclusion: If testing shows low output, high resistance, or no return current from the alternator, replacement or professional repair is typically required. Driving with a failing charging system can leave you stranded.
When to seek professional help
Timely action and safety considerations
Because the alternator supports critical systems, including ignition and fuel delivery, address suspected failure promptly. Seek professional diagnosis if you notice multiple signs, the warning light, or persistent electrical issues. A trained technician can confirm whether the alternator, belt, wiring, or regulator is the root cause and perform the appropriate repair or replacement.
Summary
On a G35, a bad alternator typically shows up first as electrical symptoms (flickering lights, dashboard warning lights, unreliable power to accessories), followed by starting or running problems (the engine cranks slowly, stalls, or loses power). Diagnostic checks focus on voltage readings with the engine off and running, belt condition, and a professional charging-system test. Prompt testing and repair are important to prevent a breakdown and ensure reliable operation.