What the Alternator Does
The alternator charges the battery and powers all electrical systems while the engine is running. Without it, the battery drains in 20-30 minutes and the vehicle dies. The alternator converts mechanical energy (from the serpentine belt) into electrical energy. A typical alternator outputs 12-14.5 volts and 80-150 amps.
Early Warning Signs
Battery/charging warning light on the dashboard (the most direct indicator). Headlights dim at idle but brighten when revving the engine. Electrical accessories (radio, power windows, heated seats) working intermittently. Dashboard lights flickering. A whining or grinding noise from the alternator area. Battery keeps dying even though it tests good. Smell of burning rubber (from a slipping belt) or hot wire.
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Battery, alternator, starter testing free with any repair. Wiring + parasitic-draw work at $120/hr.
Battery vs Alternator — How to Tell
If the car starts fine after a jump but dies while driving, the alternator is not charging. If the battery is dead but the car runs fine once jumped, the battery is the problem. We test both with a digital multimeter and a load tester. A healthy alternator outputs 13.5-14.5 volts at idle. Below 13 volts indicates failure. We also test the diode pattern — a failing diode can cause the alternator to undercharge even if the voltage looks acceptable.
Repair Cost
Alternator replacement: $350-$700 depending on the vehicle (luxury and European vehicles are on the higher end). The alternator itself costs $150-$400 and labor is typically 1-2 hours. We also check and replace the serpentine belt if it shows wear since we are already in that area. A new battery installed at the same time as an alternator failure will just die again — always test the alternator before replacing the battery.
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Battery, alternator, starter testing free with any repair. Wiring + parasitic-draw work at $120/hr. Free Uber within 5 miles if you drop off. Walk-ins welcome 7 days a week.
- 12-mo / 12,000-mi warranty
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