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Is there some way we can predict that the car alternator is about to fail in order to avoid a discharged battery situation on the road..

Although it will slow the sound of horn and will dim the headlights but is there some way we get to know about it before our journey or may be at the time of regular car service..

Is the blinking battery sign the only option..??

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up vote 5 down vote accepted

Probably not, but maybe in some circumstances. I've had 4 alternator failures in my life.

1) Toyota MR2 - Alternator diode blew up (big bang and smoke) while driving on the expressway. No prior warning. Just BANG! and was suddenly on battery.

2) Toyota MR2 - Alternator casing broke causing the alternator to bind up and jam (with loud scraping and banging noises). No warning. Perhaps if I'd have visually inspected the alternator I might have seen a crack, but the alternator is not visually accessible anyways.

3) Mitsubishi Eclipse - Aftermarket voltage gauge installed, noted that at idle the voltage was down at battery type levels (12.3 instead of 13-14). Took that as my warning and swapped the alternator. Factory gauge/light gave no warning.

4) Mitsubishi Eclipse - Voltage regulator in the above replacement alternator failed after 9 months (still in warranty, but was unable to get the aftermarket manufacturer to honor the warranty, I now ONLY buy OEM alternators). Voltage was running too high (15-16 volts). Noticed that every single warning light on the dash would glow... So, perhaps that might be a warning to keep in mind for overvoltage failures. :-)

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I have had several fail also. The usual symptom was like a light bulb, worked one minute dead the next. – mikes Dec 27 '12 at 18:48

The horn changing, and lights getting dim are not going to be the first things you would notice.

The first thing you would notice during driving would be more sluggish performance under high load, but you may already notice the car being more difficult to start.

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