YACT: Woe is me... Any way to test for failure of alternator?

[weirdichi]

My battery light just came on and I'm not sure if it's the battery or alternator. Any way to test it by myself to see if it's the alternator?

*EDIT*
Checked battery with reader while engine was on and it reades about 12.5, which is normal. The light just came on about 2 hours ago. I'm thinking it's the alternator right now. Any idea on how to make sure it's the alternator?

*Day 2*
This morning when I started the car, the battery light never came on. I drove it to work (about 5 miles) and seems normal. Could the alternator just be "hiding" its sickness from me and choosing to crap out in the middle of rush hour? If it helps, the other week while I was cleaning the car, I removed the negative from the battery when the radio was playing (one key turn away from the off position). Maybe that was what killed my alternator?

When cleaning the wires, I use water and baking soda. My friend sake Coke works also. I don't have any Coke or baking soda, so would other varieties of pop work (ie: Sprite, Root Beer, etc...)?

 

[MikeMike]

what does your voltage say on your volt meter when the car is running?
14.4 is with an alternator. your lights are much dimmer if your alt is gone.

MIKE

 

[fredtam]

If it is a newer car don't take the battery cable off to test it. nourdmrolNMT1 is correct your lights will be dimmer. An easy way to check is turn the lights on and then additional electrical devices. The lights should dim if it is the alternator. Take it to autozone or pepboys. They will test it for free.

 

[Eli]

Why would your starter being bad cause your battery light to come on?

 

[weirdichi]

Originally posted by: Eli
Why would your starter being bad cause your battery light to come on?

I thought starter and alternator were the same thing, but I just figured out that if it was my starter, I wouldn't be able to start the car.

 

[rezinn]

Take the alternator off along with the battery and have them both tested. Don't drive like that because a bad battery can kill an alternator, and vice versa. Bad wiring between either could also kill both or one or the other. Might be a good idea to test the voltage output at the alternator with the car running, and also at the battery. There should be very little difference if the wiring between them is good.

BTW, if your battery is over 5 years old, consider replacing it as it doesn't have much life ahead of it anyway.

 

[NetGuySC]

The old way was to remove the battery cables while the engine is running. If engine stops after battery cables are removed then you have a bad alternator.

 

[amdskip]

Take it to autozone and they will test it for nothing.

 

[weirdichi]

Originally posted by: NetGuySC
The old way was to remove the battery cables while the engine is running. If engine stops after battery cables are removed then you have a bad alternator.

That seems bad. Wouldn't that ruin something?? Short circuit something?

 

[Eli]

Originally posted by: weirdichi

Originally posted by: NetGuySC
The old way was to remove the battery cables while the engine is running. If engine stops after battery cables are removed then you have a bad alternator.

That seems bad. Wouldn't that ruin something?? Short circuit something?

No.

 

[fredtam]

Originally posted by: Eli

Originally posted by: weirdichi

Originally posted by: NetGuySC
The old way was to remove the battery cables while the engine is running. If engine stops after battery cables are removed then you have a bad alternator.

That seems bad. Wouldn't that ruin something?? Short circuit something?

No.

Yes. It can cause voltage spikes and hurt some electronics. I try not to do it on newer cars.

 

[Spikesoldier]

Originally posted by: amdskip
Take it to autozone and they will test it for nothing.

 

[Actaeon]

Originally posted by: Spikesoldier

Originally posted by: amdskip
Take it to autozone and they will test it for nothing.

Yep.

I thought mine was broken, had them test mine, and mine was good.

 

[Pacfanweb]

Originally posted by: fredtam

Originally posted by: Eli

Originally posted by: weirdichi

Originally posted by: NetGuySC
The old way was to remove the battery cables while the engine is running. If engine stops after battery cables are removed then you have a bad alternator.

That seems bad. Wouldn't that ruin something?? Short circuit something?

No.

Yes. It can cause voltage spikes and hurt some electronics. I try not to do it on newer cars.

Done it for years on all cars and never had a problem. Just remove the negative cable while the engine is running; if it cuts off, the alternator is definitely bad.
I know all the repair manuals say don't do it, but thousands of mechanics do it all the time with no problem.

 

[Eli]

Originally posted by: fredtam

Originally posted by: Eli

Originally posted by: weirdichi

Originally posted by: NetGuySC
The old way was to remove the battery cables while the engine is running. If engine stops after battery cables are removed then you have a bad alternator.

That seems bad. Wouldn't that ruin something?? Short circuit something?

No.

Yes. It can cause voltage spikes and hurt some electronics. I try not to do it on newer cars.

I did think about that, but as long as you remove the negative first... it shouldn't.

The electronics are feeding off the alternator(assuming its working) anyway, the battery is just acting as a big capacitor.. so...

 

The old way was to remove the battery cables while the engine is running. If engine stops after battery cables are removed then you have a bad alternator.

What the HELL ARE YOU PEOPLE SMOKING, removing either the positive or negative battery cables while the engine is running will immediately destroy the alternator along with the ECM.


I'm surprised at you Eli, I thought you knew better.


To test the alternator, check battery voltage with a volt/ohm meter with the engine off, it should read about 12.5 V, start vehicle, it should read between 13.2 and 14.7, anything lower or higher indicates alternator failure.

 

[Red]

I knew my alternator was bad when I hooked up my new battery and smoke started coming out of the alternator, with the car off. If yours is doing that, it's probably bad =)

 

[Viperoni]

Originally posted by: Roger

The old way was to remove the battery cables while the engine is running. If engine stops after battery cables are removed then you have a bad alternator.

What the HELL ARE YOU PEOPLE SMOKING, removing either the positive or negative battery cables while the engine is running will immediately destroy the alternator along with the ECM.


I'm surprised at you Eli, I thought you knew better.


To test the alternator, check battery voltage with a volt/ohm meter with the engine off, it should read about 12.5 V, start vehicle, it should read between 13.2 and 14.7, anything lower or higher indicates alternator failure.

That's exactly what I thought as well. I doubt it'll immediately destroy stuff, but from what I've read, it's a big no-no.

Best way is definetely to break out the voltmeter

 

[weirdichi]

Originally posted by: Roger

The old way was to remove the battery cables while the engine is running. If engine stops after battery cables are removed then you have a bad alternator.

What the HELL ARE YOU PEOPLE SMOKING, removing either the positive or negative battery cables while the engine is running will immediately destroy the alternator along with the ECM.


I'm surprised at you Eli, I thought you knew better.


To test the alternator, check battery voltage with a volt/ohm meter with the engine off, it should read about 12.5 V, start vehicle, it should read between 13.2 and 14.7, anything lower or higher indicates alternator failure.

Wouldn't matter when I tested the battery (while the engine is off)? For example, testing it when it was sitting outside all night as opposed to testing it after I have just driven it?

Also, this morning when I started the car, the battery light never came on. I drove it to work (about 5 miles) and seems normal. Could the alternator just be "hiding" its sickness from me and choosing to crap out in the middle of rush hour? If it helps, the other week while I was cleaning the car, I removed the negative from the battery when the radio was playing (one key turn away from the off position). Maybe that was what killed my alternator?

 

[CraigRT]

12.5 is not normal for a running car
should be LOWEST at 13, around 14V.

 

Also, this morning when I started the car, the battery light never came on. I drove it to work (about 5 miles) and seems normal. Could the alternator just be "hiding" its sickness from me and choosing to crap out in the middle of rush hour? If it helps, the other week while I was cleaning the car, I removed the negative from the battery when the radio was playing (one key turn away from the off position). Maybe that was what killed my alternator?

That's an excellent way to destroy the ECM (electronic control module) in your vehicle, never, ever, EVER remove either battery cable when the key is in the ignition.

Thoroughly clean your battery terminals until you see shiny lead (top post), a corroded terminal can cause the alternator to fail to see battery voltage, thus causing a no charge condition.

 

[notfred]

Originally posted by: weirdichi
I thought starter and alternator were the same thing...

Not to be rude or anything, but just take the car to a mechanic and say, "the battery light is coming on, can you tell me what's wrong with the car?", because you obviously don't know what you're doing.

 

[weirdichi]

Originally posted by: notfred

Originally posted by: weirdichi
I thought starter and alternator were the same thing...

Not to be rude or anything, but just take the car to a mechanic and say, "the battery light is coming on, can you tell me what's wrong with the car?", because you obviously don't know what you're doing.

Damn, people need to quit with the bashing, name calling, etc that I have seen the last 4-5 months on here. Thanks for the mechanic advice, but I could've done without the last part of your comment. I've researched this, called up mechanics, and talked with friends who are knowledgable about cars. Please, if you feel like you need to just add a little something at the end of your comment to make you feel better, don't reply to other people's threads when all they want is genuine help.

 

[Titan]

if it's a newer car, chances are the light or some sensor is broken. The alternator istelf should be fine, but if it's dying, you'd be losing juice and if it's dead your car wouldn't run for more than a few miles with light on before the battery drained. The belt could cause fluctuations, but if you don't notice any power drains, the alternator is most likely fine. In newer cars, stupid lights and sensors often break more than the parts themselves, and can be more of a pain to fix.

my 2¢

 

[weirdichi]

Originally posted by: tkotitan2
if it's a newer car, chances are the light or some sensor is broken. The alternator istelf should be fine, but if it's dying, you'd be losing juice and if it's dead your car wouldn't run for more than a few miles with light on before the battery drained. The belt could cause fluctuations, but if you don't notice any power drains, the alternator is most likely fine. In newer cars, stupid lights and sensors often break more than the parts themselves, and can be more of a pain to fix.

my 2¢

The car is a 91 Integra. I think it IS the alternator, I just want to make sure. I'll clean the wires on the battery first and measure the voltage. What I am wondering is if there's a way for me to measure the voltage on the alternator itself. Any ideas?

When cleaning the wires, I use water and baking soda. My friend sake Coke works also. I don't have any Coke or baking soda, so would other varieties of pop work (ie: Sprite, Root Beer, etc...)?