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Discussion Starter #1
I have a 2003 Ody. Today, driving around town, I noticed the Battery Light was on. But also, the warning lights for doors open were on, all of them, and under that icon, Brake Lamp was also lit up. I know Hiowe Silver (
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my van) is trying to tell me something is wrong. anyone here know what that might be? sorty gor the messy dash. and the SRS light was NOT on earlier today. I had my wife snap.a pic and send it to me at work. don't think she followed my detailed direction.
 

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When multiple lights are on like that it's usually a battery/alternator issue.
 

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With the engine running, a voltmeter (or battery tester) should read around 13.7V or greater. I think max of 14.4V . A 12v car battery should be 12.7V ful (test when the car has been off for awhile. Will read higher if it was started/charged recently)l, but a 12.3V should still be fine. I'm going to assume that the battery is starting the car fine

Most car part stores will do battery testing or alternator testing for free.
 

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Most likely the alternator. Once you check the voltage if it is low you can pull the alternator and replace the brushes. That is if the alternator isn’t making any grinding/rumbling noises indicating a bad bearing.
Some will say just get a new alternator but I pulled mine cleaned the copper rings with scotch rite and replaced my brushes with one from Honda. That was 6 years ago.
I rebuild all my starters and alternators on my cars and motorcycles. Parts store alternators and starters are crap.
If you do buy a replacement make sure it is a Denso, much less trouble than a parts store rebuild.
 

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You can test the alternator by disconnect the battery while the engine is running.
Definitely don't do that.

It might work. But there is a good chance it will damage your alternator or even other electrical components throughout your car.

Another thing that may damage your alternator is taking it in to your parts store for testing.

BTW, I've had both of those things happen to me. First one was accidental, where I had just pushed the battery terminal down onto the post while debugging something, and it momentarily came loose, frying the voltage regulator (part of the alternator).

Just a voltmeter on the battery posts when the engine is running should tell you what you need to know. And that's completely safe. Easy too.
 

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Another thing that may damage your alternator is taking it in to your parts store for testing.
Can you explain? I agree with the rest of your post but found this one unusual. Unless they're disconnecting the battery or load testing the alternator.

I have a shumaker battery tester that's really a voltmeter and toaster appliance. Pressing the switch applies the toaster coils, to test the voltage and cranking amps of the battery. Instructions state to never load test with the engine running, and refer to voltmeter only to test for alternator functionality.
 

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Can you explain? I agree with the rest of your post but found this one unusual. Unless they're disconnecting the battery or load testing the alternator.
Mainly that they can screw anything up, and are likely to have very little idea about what they're doing. Just hooking something up wrong can easily do it. They look up your alternator, based on the year+model of your car, the computer tells them what to hook up, etc. So easy a trained monkey could do it. And a trained monkey could also fry your alternator.

I avoid those places unless I feel I have nothing to lose, and when I do go in there, I ask to watch the test. Partly due to curiosity of how they do it, and also so I'll have a better understanding of how much to believe any result they give me. Sometimes a little scary watching them fumble around with the equipment. Some are great though.

One time, I'm convinced they damaged a working alternator that I had just taken in to check before I knew better.

And then that alternator (VR) that I mentioned was damaged when the battery terminal loosened momentarily, was tested GOOD by my local pep boys. I do give them credit for trying and getting it on the machine and tested, even though the result was bad. That was from my air cooled 911, where the alternator pulley and engine-air-cooling fan are one and the same. They were pretty excited to get that thing on the machine, and I was impressed with their curiosity. We were all pretty impressed at the resulting air flow. But they tested it as GOOD, and nothing made sense (made my debugging difficult until I figured I should ignore that test result), and nothing worked until I eventually replaced the alternator with a new one, and everything worked.
 

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Definitely don't do that.

It might work. But there is a good chance it will damage your alternator or even other electrical components throughout your car.
Do you know what typical components that goes bad in an alternator?
Do you even know what you are talking about?
You are undermining the engineers of the alternator and vehicle who designed it to take into consideration what happens when the battery failed to absorb the charge. On the contrary, what happens when the battery is fully charged and no longer takes charge?

The main and probably only reason there’s a battery is to provide the initial current to the starter crank up the engine and ignition/fuel pump to start the vehicle in short.
Why do you think push starting a vehicle with a dead battery works/runs when the battery cells are no longer charging?

I’ve rebuilt alternators and starters before and done this test in short ran without battery (after starting up) many times. Starts vehicle by rolling down hill manual and automatic transmission as well.
 

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I most definitely do know what I'm talking about. How about you? Are you an expert in this field because you pulled a cable off your battery and were lucky to have no problems?

Since you asked ...

I have rebuilt many alternators. I know exactly what fails and how to test each component. Search for my posts on here regarding that. I have a Ph.D. minor in EE from the second best engineering school in the world. And 3 more degrees from the best engineering school in the world. You might learn something here if you pay attention.

Here's a good and interesting page on alternator history and basics of how they work and have worked through the ages. The disconnecting from the battery thing was safe in the olden days. Not so safe now. Unlike much of the info you find on the web, that page seems to have been written with solid engineering understanding (vs. mechanic-level understanding, which is valuable, but different).


Looks to me like good info from a good company.

From that page, "DC generators do have a couple of advantages over alternators however. Reverse polarity or strong electrical spikes are far more likely to damage an alternator than a generator. Furthermore, in the case of a dead battery, a DC generator can still produce power, whereas an alternator may not or may damage itself due to high voltage. "

Again, "may or may not." You don't know for sure. One or more safely done tests does not prove it to be a good idea. Even disconnecting jumper cables from a running car after jump starting it can cause a voltage spike that will damage electronics, and for that reason, some manufacturers (my BMW, for example) list steps in the owner's manual to dissipate that spike (turning on the rear window defroster).

If you want to do that test yourself on your own car, and feel you understand things well enough, go ahead. It may be just fine. But it is not necessarily good advice to offer to other people who may not be able to make an informed judgment. And that's why I figured I'd respond as I did above.

And think about it ...
Your suggestion is to remove the cable while the car is running, with the logic that if the engine (now with no battery to provide voltage, and now only the alternator) then dies, it must be because the alternator is faulty. And if you're lucky and your alternator does not die, you may have confirmed it good, suffered no extra failure, and can continue on your search for the real problem. Fine.

But what if you're unlucky and the alternator is damaged by your test? Well if you believe in the test, you may incorrectly conclude that your test is fine and that it confirmed the alternator was already bad (maybe as a common example, it previously had worn brushes, and the test blew a diode). And you'll continue to believe the test is safe, which would be incorrect.

So basically, if you believe in the test, you may not come across evidence to change your mind on it, unless you start pulling cables on perfectly running engines as standard practice. Please don't do that.
 

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Haha.. flexing your muscles. I’ve done just so many times and it hasn’t caused any problem yet. You still undermine the engineers, but wait you claimed you’re one. How interesting.

We may not agreed on this and may never will.
I’ve seen many people with degrees doesn’t no much in practical things. So it’s meaningless to flex your muscles.
 

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Do you know what typical components that goes bad in an alternator?
Do you even know what you are talking about?
You are undermining the engineers of the alternator and vehicle who designed it to take into consideration what happens when the battery failed to absorb the charge. On the contrary, what happens when the battery is fully charged and no longer takes charge?

The main and probably only reason there’s a battery is to provide the initial current to the starter crank up the engine and ignition/fuel pump to start the vehicle in short.
Why do you think push starting a vehicle with a dead battery works/runs when the battery cells are no longer charging?

I’ve rebuilt alternators and starters before and done this test in short ran without battery (after starting up) many times. Starts vehicle by rolling down hill manual and automatic transmission as well.
 

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I have done that test on my old cars before with not much harm done. However, it does not mean that its the correct way to test an alternator. Particularly with vehicles now that are heavily dependent on electricity to run it, why risk frying any components with your antiquated method. Its better to give advise or recommendation that will not risk damage to the car or person. Why insist that its a good way to test it knowing that a messed up voltage regulator in that alternator can run the car and fry the system at the same time with a voltage spike. Its poor advise so just stop selling it. Simple test without risk of damage can easily be done. an example: https://www.familyhandyman.com/automotive/how-to-test-an-alternator/
 

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Discussion Starter #16
since I have several knowledgeable fellows here, I am replacing the alternator. should I also replace the belt? current belt has over 100k on it.
any other components that are highly logical to replace in this process?
 

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Are you talking about the alternator belt? I would replace it if that's what you are talking about.
 

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100k miles on the old serpentine belt is about recommended (usually the same interval as the timing belt/ water pump).
Not worth the trouble to reuse the old belt.
 

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Glad you agree it worked and not much harm done. I only post that suggestion once. I don’t see any harm in it.
I'm sure you don't see any harm, and, if there is , you won't be paying for it. :eek:
Bad advice on the modern electronic controls in today's vehicles, esp Hondas, which are very susceptible to voltage spikes and levels.
Keep your interest in autos up, but DO NOT give out very potential damaging ignorant advice.
Removing the battery on old DC generators while the engine was running., like on a 55 Chev, didn't do any harm and many did that while doing a drag race, including me.
If you want to give out tips like that, at least you could say 'well, it worked OK on my 55 Chev or similar' before you say 'TRY IT'!
Buffalo4
 

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since I have several knowledgeable fellows here, I am replacing the alternator. should I also replace the belt? current belt has over 100k on it.
any other components that are highly logical to replace in this process?
Yes indeed !! You may even want to check to see if the belt tensioner for that belt needs to be replaced also.
Buffalo4
 
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