Rick's Free Auto Repair Advice

Signs of a bad alternator

Signs of a bad alternator — What to look for

Electrical signs of a bad alternator

Slow cranking can be a sign of a bad alternator

• If the alternator isn’t recharging the battery, the battery will be weak.
• A shorted diode in the alternator can charge the battery when the engine is running but create a large enough battery drain to kill the battery overnight.

Dim Headlights while stopped can be a sign of a bad alternator

A good alternator should be able to produce enough power at idle to keep your headlights at full brightness. If your headlights dim considerable when at a stop light, get your charging and battery tested.

Electrical accessory malfunction can be a sign of a bad alternator

Electrical accessories like heated seats, heated mirrors, or a rear window defogger consume a lot of power. If they activate and immediately shut off, that can be a sign of low power. Have the charging system tested.

Mechanical signs of a bad alternator

alternator rebuild kit

Alternator rebuild kit

Alternators contain two bearings, a brush set and an over-riding clutch. When those parts wear, they create growling or squealing noises; signs of a bad alternator.

Use an automotive stethoscope to check the sound of the front and rear alternator bearings. If you hear growling or one bearing is considerably louder than the other, chances are one of the bearings is failing.

A burning smell can be a sign of a bad alternator

An overheated alternator can melt the insulation off the stator or rotor windings. That will produce and electrical burning smell.

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Posted on by Rick Muscoplat

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