The alternator is the heart of your vehicle's electrical system — while the engine is running, it produces the electrical current that powers everything (lights, fuel pump, ignition, climate control, computer modules) and recharges the battery for the next start. A failing alternator turns a healthy battery into a no-start within a day or two. Frank's Automotive in New Braunfels diagnoses charging-system problems with proper equipment so you replace the part that's actually failing — not the battery first, then the alternator a week later.
What's involved
A charging-system diagnosis at our shop:
- Resting voltage at the battery (engine off): should be 12.6 V or higher
- Engine-running voltage: should rise to 13.8–14.7 V at idle, holding steady as load is added (turn on headlights, blower, defrost)
- Ripple test with a scope or quality multimeter — diodes inside the alternator can fail without dropping voltage, and the AC ripple they produce wrecks computer modules over time
- Belt and tensioner check — a slipping or worn serpentine belt looks like an alternator failure
- Connector and ground inspection — corroded battery cables, loose grounds, and bad alternator connectors mimic alternator failure
If the alternator needs replacement, we install an OEM-equivalent unit, and we replace the serpentine belt and tensioner at the same time if either is questionable — they're already off, and combined labor is cheaper than coming back in 6 months.
When to bring it in
Symptoms of a failing alternator:
- Dashboard "battery" or "ALT" warning light, sometimes intermittent
- Dimming headlights at idle that brighten when you rev the engine
- Electrical accessories acting strange — flickering interior lights, fluctuating gauges, radio resetting
- Slow crank that gets worse over a couple of days (battery being drained instead of charged)
- Battery keeps going dead even after replacement — that's the alternator, not a bad new battery
- Burning rubber smell from a slipping belt
- Whining that rises with engine RPM
Don't drive past a charging warning light expecting to "make it home" — once the battery runs out, the engine cuts and you lose power steering and power brakes. Get it diagnosed before that happens.
Why Frank's for alternator repair
Our service techs are ASE Certified, we have the diagnostic equipment (scopes, load testers, current clamps) to test alternators properly — not just guess based on dashboard symptoms — and we use OEM-equivalent replacement units that match your vehicle's output rating. The work is covered by our 24-month / 24,000-mile warranty.
Call us with the symptoms and we'll get the charging system tested same-day in most cases. Request an appointment or call (830) 627-3939.