How can I make sure I have a bad altenator?

I don’t care about credit but as far as I can see nothing has been solved.

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Perhaps the car can’t yet be driven, because OP is only 17 years old, according to them

Yep actually that is true probably gonna get my permit by the end of January. But anyways like I said before I’m going to just replace the alternator and go from there.

As for that permit . . . are you in a state where you are required to attend a driving school for x number of hours of classroom and behind the wheel training?

Or is your dad/mom allowed to teach you how to drive?

You can get a permit without the class and have to have the permit for 9 months then have to take a 3 week class before you get a provisional hold that for 18 months to get full drivers license.

Good idea when you replace the alternator to keep the old one long enough to make sure the new one cures the problem. Don’t turn it in for the core charge right away.

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Will do thank you. I should be able to return the new one if the alternator isn’t the problem.

Oh one last quick thing I forgot to mention it idles about 1500 rpm if that means anything.

Even after it’s reached operating temperature?

No obvious vacuum leaks?

Have you cleaned the throttle body yet?

Does this engine have a idle air control valve?

No I haven’t cleaned it. Also I didn’t let the car heat up much only kept it on for around 10 mins. I’ll check it again when I get the chance and let it heat up more. As for idle air control valve I don’t know if it has one I’ll have to check because I have the lowest model of the car. As for vacuum leaks I don’t belive so because no codes come up for a vacuum leak but I guess it might not always come up.

@db4690, thanks for the feedback. I think if an OP wishes to give credit to someone who replies, that’s up to them. If someone surfed into this thread looking for answers, I think they would see the check mark was only one of several factors they’d consider in deciding whether there was actionable info here. A lot of people don’t even use the solution option. We’ll see how it plays out.

Before removing the alternator you should verify that the battery warning light circuit is working correctly. The real problem may be a bad wire connection between the light and the alternator. Power from the ignition switch passes through the warning light when the ignition is ON. That power is passed on to the alternator field circuit which needs to be energized by the power. If power can’t get to the field windings then there is no output from the alternator. The lead that ties to the warning light can be tested by grounding the connection that ties to the alternator. If the circuit is good the warning light will turn on since it is in series with the circuit. You need to make sure you have the correct lead if you do that. The other lead is hot to the battery and shorting it to ground will cause a short and blow fuse. A safer way to make the check is to check the voltage of the wire connection.

Ok so I had the alternator and battery tested at autozone and they both passed BUT I got a new altenenator anyways because I was told that the old one may not work underload. So after putting in the new alternator I tested the voltage. I had started with around 12.3 volts because I didn’t charge the battery lately. Then I put on everything I could electrical and the voltage was around 11.11 - 11.30 and just kept on going between that for around 10 or 15 mins. After that the voltage stayed at 11.56 without changing. I also noticed the battery light does come on but only when it hits a certain RPM when I rev the engine. Then after I stop reving the engine it almost cuts out and the battery light goes out. Its also a manual car. I have a few youtube videos linked below.

So what should I do next?


The engine is likely cutting out because the battery voltage is dropping too low and the alternator is not charging. Usually around 10 something they may cut out or stall.

Turn the key to the RUN position; engine not running.
Touch the alternator pulley with the tip of a screwdriver.
You should feel a magnetic attraction from the alternator pulley.

If so, this means (usually) the alternator is charging.
You then need to check the circuit between the alternator and battery. I think this was mentioned by Cougar at one point.

I think your car uses a plastic encased fusible link. That should be high amperage in the underhood fuse box. Remove it and look very closely at the wire across the top of the link.
Sometimes with electrical issues, shorts, or age the high current heat will melt the solder at the ends of the wire and cause a poor or erratic connection.

Note the kit below. It will resemble one of the 4 colored blocks in the kit. They have a clear plastic lid on them. If the solder is melting you may see what appears to be a small ball on one or both ends of the wire. Hope that helps.

http://www.autozone.com/electrical-and-lighting/fuse/bussmann-fuse/32387_131734_0_87767?checkfit=true

I found this thing attached to the postive terminal that says 120A ALT. So thats for the alternator right? Is it blown it looks like it to me just want to make sure because I don’t know to much yet. I feel kinda stupid now if thats the problem :sweat_smile: I saw this thing before but didn’t think much of it till now. Also I put a screw driver up to the alternator pulley like you said and yes it is magnetic just slightly though.

Use a volt meter or test light on the positive stud on the back of the alternator to see if there is power with the engine off. Next measure the voltage at the positive stud with the engine running.

Put the black lead of your voltmeter to the negative post on the battery. Put the red lead to the nut in the lower part of your picture. If around 12 volts, the fuse is good. If zero, odds are it’s bad. You can check it with an ohmmeter as well.

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With the car not started it doesn’t light. With it started it lights. As for the test with the multimeter that OldcarsRbest said to do on the nut of that fuse on the postive cable it measures 2.12 volts so I’ll order a new one because I am pretty sure that means its no good.

Yes the fuse appears to be blown, in the future check that there is power at the alternator stud before removing the alternator, no power indicates that it is not connected to the battery.

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Here’s what to typically expect: With the battery charged, the battery posts should measure about 12.6 volts with the key removed, engine off, everything turned off, and all the doors closed. Then after starting it up, with the engine running it should measure 13-15.5 volts. Towards the higher voltage range when first starting the engine, and lowering toward the lower range of values the longer the engine runs and the battery becomes more fully charged.

One easy way to test this at night is to observe the headlights with the engine off vs engine on. They should be noticeably brighter with the engine on.