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  #16  
Old 07-27-2007, 05:08 AM
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Quote:
Originally Posted by blue thunder
I'm having the same issue as Idaho biker girl a few posts back. Two nights ago i got in my car to go home and noticed the illumination light on the dash seemed weaker than usual. I drove home with no problem. Today on the way to work the dash lights came on and stayed intermittedly. I tried a test someone said to try. I started the car and then disconnected the negative battery cable and the engine stalled immediately. I was told this means the alternator is bad. Then I drove home tonight with the dash lights coming on and off the whole way. I then got my multimeter and checked the voltage and it read around 12 amps non-running which means the battery is fully charged right? Could my alternator be flaking out and still be charging my battery? I have one ordered for thurs. although I haven't paid yet. Any advice or experience appreciated. Thanks.

Mike
Pete,

The first sentence in the thread which you have omitted and which tells all, regardless of the rather confused description which follows, reads:-

"I'm having the same issue as Idaho biker girl a few posts back."

Also note:-

"Today on the way to work the dash lights came on and stayed intermittedly."

" Then I drove home tonight with the dash lights coming on and off the whole way."

N.B. The lights came on, i.e. were not switched on.

I and obviously others here, have been able to interpret the description, having become used to some having problems when describing faults.

My object has been to prevent the enquirer becoming involved in fruitless testing, based on irrelevant voltage figures. It is most unfortunate that matters have become controversial as a result of misunderstandings and in this context touches of sarcasm are not helpful.

Unlike another thread, no one is in fact wrong here and all have simply been misunderstood.

Cheers, Trevor.
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  #17  
Old 07-27-2007, 07:44 AM
ItsPeteReally ItsPeteReally is offline
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Ah! a truce

The sad part of it all is that we may have driven the original poster away.

We may never know whether or not his alternator charging warning light was ever illuminated, or what voltage was developed across the battery terminals.

It may well have been that he had a defective alternator, but he could possibly have had a circuit continuity problem elsewhere.

I will certainly be very careful about what (and how) I post in the future, my only concern was to try and prevent him from spending over $100 on a new alternator if he didn't need one.

Pete
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  #18  
Old 07-27-2007, 12:18 PM
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A battery can read ? when fully charged??

Quote:
Originally Posted by blue thunder
I'm having the same issue as Idaho biker girl a few posts back. Two nights ago i got in my car to go home and noticed the illumination light on the dash seemed weaker than usual. I drove home with no problem. Today on the way to work the dash lights came on and stayed intermittently. I tried a test someone said to try. I started the car and then disconnected the negative battery cable and the engine stalled immediately. I was told this means the alternator is bad. Then I drove home tonight with the dash lights coming on and off the whole way. I then got my multimeter and checked the voltage and it read around 12 amps non-running which means the battery is fully charged right? Could my alternator be flaking out and still be charging my battery? I have one ordered for thurs. although I haven't paid yet. Any advice or experience appreciated. Thanks.


Mike
A battery will read 12 volts when fully charged. When working properly, it will have the cranking power it was designed to have. It can also read 12 volts when it is not fully charged because of the construction of the battery cells. under a load it will not read 12 volts when it is not fully charged, again because of the construction of the cells in the battery.In reality the best way to check out this intermittent problem is with a volt meter. When the goofy red lites all come on, open the hood with the motor running, of course and check the voltage at the battery terminals. you should get 12 volts. if you are lucky enough to have all those red lites go off while you are driving, stop the car, but leave the motor running. raise the hood and check the voltage at your battery terminals. You will see about 14 volts which is the output of the alternator at this time. Congrats! you have found the problem. Since all the voltage and regulator controls are in the alternator itself, the alternator has to be replaced! Why?? because you want the alternator to work all the time not just intermittently. It is on the way out and will not work at all soon! You can also trust some of us that have gone through this and just replace the alternator to start with, but it is a bunch of fun to work it out yourself!
Good luck with your SVX. (Don't we just love these cars!!!!)
Keith (77 year old shade tree mechanic)
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  #19  
Old 07-27-2007, 07:59 PM
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Firstly please be sure that I am not trying to extend an argument, but do wish to amplify the detail in respect of that which has proven a never ending problem having considerable technical interest.

The suggestions made here is that a faulty alternator can be detected using a DC voltmeter, because the output measured across the battery, will not be close to 14 volts, if the machine is defective.

It is fact that members here have had an alternator checked by professionals after experiencing the flashing trouble lights problem, then have been advised that the alternator is OK. One would expect that the output voltage has been measured under load by way of a test, but one must presume that the procedure has not detected an AC component in the output, due to only DC test gear being employed.

My contention is that the alternator could produce adequate voltage, albeit at reduced current, even though a faulty diode may exist, but at the same time produce an alternating current component within the output. N.B. --- Hence my reason to dispute the validity of a simple DC voltage test.

The alternator is in effect a three phase device, incorporating nine diodes in rectifier bridge networks, so that the failure of a single diode may only somewhat reduce output current, and the voltage regulator could compensate in respect of voltage.

We need someone who has an alternator with the fault in question, able to carry out proper tests and experiments, in order to be able to exactly confirm the several factors which apply. The understanding required, will likely be above the head of the average auto electrician.
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Last edited by Trevor; 07-27-2007 at 08:03 PM.
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  #20  
Old 07-29-2007, 12:45 AM
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Quote:
Originally Posted by Trevor
The suggestions made here is that a faulty alternator can be detected using a DC voltmeter, because the output measured across the battery, will not be close to 14 volts, if the machine is defective.

It is fact that members here have had an alternator checked by professionals after experiencing the flashing trouble lights problem, then have been advised that the alternator is OK. One would expect that the output voltage has been measured under load by way of a test, but one must presume that the procedure has not detected an AC component in the output, due to only DC test gear being employed.

My contention is that the alternator could produce adequate voltage, albeit at reduced current, even though a faulty diode may exist, but at the same time produce an alternating current component within the output. N.B. --- Hence my reason to dispute the validity of a simple DC voltage test.

The alternator is in effect a three phase device, incorporating nine diodes in rectifier bridge networks, so that the failure of a single diode may only somewhat reduce output current, and the voltage regulator could compensate in respect of voltage.

We need someone who has an alternator with the fault in question, able to carry out proper tests and experiments, in order to be able to exactly confirm the several factors which apply. The understanding required, will likely be above the head of the average auto electrician.
One of us is able to use a simple test to check an alternator with a DC voltmeter.
None of the people here care about how a diode works. If an alternator doesn’t charge the battery, the alternator has to be replaced. . I have a lot of education and years of experience including one electronics school that began with basics including how every part of an alternator is made, the composition of batteries, and eventually getting to electrical schematics that you couldn’t put on a a sheet of paper as big as a double page of a newspaper. Just one school was 8 hours a day for a full year. I would be void of logic if I couldn’t tell that the alternator was bad if all my red lights came on and I put a voltmeter on it and only got the 12 volts from the battery. When I drove it again and the red lights went off, checked it with the lights off and the output was 14 volts. When 14 volts are put into a 12-volt battery, it charges the battery, period. More logic! I do not need all my education and experience to find out why my alternator doesn’t work.I only need to know to set the meter for dc volts, put the red lead on the positive battery terminal and the black lead on the negative terminal. I don’t even care why the alternator doesn’t work. Why, because to replace the parts in our old alternator would cost at the least $2,000.00 at the Subaru dealer. Several of the parts cost more each than replacing the whole alternator! More logic, just pay the $200 and get a whole new alternator at the same Subaru dealer!
You might be amazed at how little electrical expertise these auto “mechanics” actually have!
KISS Keep It Simple, St----
Keith
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  #21  
Old 07-29-2007, 08:36 AM
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Quote:
Originally Posted by kwren
...None of the people here care about how a diode works...Keith
You are clearly not speaking for yourself (or me) and there is no need to speak for others. Especially, if you are going to disparage their intelligence and/or curiosity.

A generator produces direct current (DC) which has a fixed polarity, + and - are always on the same side (wire). An alternator is more efficient than a generator, but produces alternating current where the polarity (+/-) switches as the armature is turned. A diode is like a one way street sign, or a turnstile. It allows current to flow in one direction only. By placing a diode on both sides of the output an alternator can be polarized to supply a DC system.

A diode can fail in 2 ways.

It can stop passing current in either direction. If only one fails, this will result in only half of the output being supplied to the system. Because there will still be voltage of the correct polarity, this condition is difficult to test and is the reason why so many bad alternators are tested and proclaimed good.

A diode can also fail by allowing current to pass in both directions. Diodes are designed to resist a certain amount of reverse current flow. This is called the reverse breakdown voltage. If it's capasity to resist this flow is diminished, things will not be well. The symtoms of this are difficult to predict, except that the greater the load, the greater the symtoms will become. This condition will diminish a battery's ability to accept and deliver a charge and eventually render it useless. Note that such a battery might provide acceptable voltage readings if not under load.

What Trevor is suggesting is that this condition can be discovered by using a voltmeter set to A/C to find what he refers to as 'alternating current component'. Prior to reading his repeated suggestion in this forum, I was unaware of any test for this condition. I have not had the opportunity to perform this test, but it does make sense. Historically, a repair would envolve replacing both the battery and the alternator. Usually one, then when that didn't work, the other.

Charl

Edit:corrected spellings.

Last edited by cdvs; 07-29-2007 at 01:04 PM.
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  #22  
Old 07-29-2007, 11:36 AM
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I am sorry

Charl, you are right to say, “You are clearly not speaking for yourself (or me) and there is no need to speak for others.” But not right to say “Especially, if you are going to disparage their inteligence (Intelligence) and/or curiousity. (Curiosity)…. I was certainly not intending to disparage anyone here but was trying to make it simple for maybe the one or two SVX owners that are nor predisposed with the workings of the internal components of their alternator.. Offending anyone was certainly not my intent and I apologize to anyone that I inadvertently offended. I misspoke and I am sorry
Take care
Keith
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  #23  
Old 07-29-2007, 01:43 PM
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Keith,

Thanks for the spelling corrections.

I, personally, have always found KISS to be a disparaging commentary. It has it's roots in Occam's Razor; a principle asserting that one should not complicate things more than is required to achieve an explanation. There is nothing stupid about it.

While I appreciate your attempt to simplify the diagnosis, it falls short of being complete and will, in many cases, lead to the wrong conclusion. It is correct that if, with the engine running, a voltmeter set on DC reads less than 13.8 volts there is a problem with the alternator, or it's integrated components. However, as detailed in my previous post, there are at least 2 conditions where a 'good' reading would be shown, despite existing faults.

Sometimes, things are not as simple as we might like them to be.

Charl
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  #24  
Old 07-29-2007, 05:40 PM
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Quote:
Originally Posted by kwren
One of us is able to use a simple test to check an alternator with a DC voltmeter.
None of the people here care about how a diode works. If an alternator doesn’t charge the battery, the alternator has to be replaced. . I have a lot of education and years of experience including one electronics school that began with basics including how every part of an alternator is made, the composition of batteries, and eventually getting to electrical schematics that you couldn’t put on a a sheet of paper as big as a double page of a newspaper. Just one school was 8 hours a day for a full year. I would be void of logic if I couldn’t tell that the alternator was bad if all my red lights came on and I put a voltmeter on it and only got the 12 volts from the battery. When I drove it again and the red lights went off, checked it with the lights off and the output was 14 volts. When 14 volts are put into a 12-volt battery, it charges the battery, period. More logic! I do not need all my education and experience to find out why my alternator doesn’t work.I only need to know to set the meter for dc volts, put the red lead on the positive battery terminal and the black lead on the negative terminal. I don’t even care why the alternator doesn’t work. Why, because to replace the parts in our old alternator would cost at the least $2,000.00 at the Subaru dealer. Several of the parts cost more each than replacing the whole alternator! More logic, just pay the $200 and get a whole new alternator at the same Subaru dealer!
You might be amazed at how little electrical expertise these auto “mechanics” actually have!
KISS Keep It Simple, St----
Keith
Keith,

I completely reject your confrontational and objectionable post. You boast “I have a lot of education, etc., etc.”, but it is apparent that this did not include appreciation and understanding of the written word.

As the ball is in my court, I feel free to return the volley and point out that I have designed and drawn schematics which would cover the whole of many newspapers and did in fact fill several filing cabinets. These original complex designs, were for hydro electric power stations, industrial complexes, hospitals etc. In anticipation of further comment, I add that the automatic starting and control of engine - alternator, mains failure equipment was involved, exactly meeting the criteria of this thread.

Please read what I have said again carefully and slowly. You may desire to “KISS”, but this problem is only simple to those who understand AC theory, i.e. something normally outside of the scope of auto electricians and I must now conclude also yours. This fact does not amaze me.

N.B. What is being discussed here is an exact fault, which can be confined to, and only becomes apparent, due the combined intermittent illumination of several trouble lights. Not a fault simply involving the DC output of an alternator.

The problem involves a test circuit linking all the test lamps together via blocking diodes, so that a voltage can be provided as a lamp test at start up. If this circuit receives a reverse voltage the lamps will illuminate under normal conditions, hence the fault condition being considered here. The fault will not be necessarily be indicated by the steady illumination of the battery/charge fault indication lamp or any of that which you propose as a test procedure.

Trevor.
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  #25  
Old 07-29-2007, 06:41 PM
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A great example!

Trevor,
This latest post of yours explains how a person can be educated and still void of logic. I originally took the stand that if the alternator on a car doesn't work, just replace it. For the super educated like you, and seriously I am impressed, I appreciate your desire to continue with all the cow pats you accumulated as a child. Since I am not personally void of logic, when I checked my alternator with a multimeter and found it was erratic, sometimes charging, and sometimes not charging, and since i need my car to start and run every day, silly me, I just replaced the alternator. Maybe everyone else on the network will be impressed with your credentials, as I also am, but I would probably be more impressed with you if you had enough common sense to just change your alternator if it doesn't work. Gee, I always get back to logic. When I was a kid, I missed all the cow patties, but I did catch the one about having enough sense to come in out of the rain.
Thanks for taking the time to keep us up to date!
Keith
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  #26  
Old 07-29-2007, 11:55 PM
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Quote:
Originally Posted by kwren
Trevor,
This latest post of yours explains how a person can be educated and still void of logic. I originally took the stand that if the alternator on a car doesn't work, just replace it. For the super educated like you, and seriously I am impressed, I appreciate your desire to continue with all the cow pats you accumulated as a child. Since I am not personally void of logic, when I checked my alternator with a multimeter and found it was erratic, sometimes charging, and sometimes not charging, and since i need my car to start and run every day, silly me, I just replaced the alternator. Maybe everyone else on the network will be impressed with your credentials, as I also am, but I would probably be more impressed with you if you had enough common sense to just change your alternator if it doesn't work. Gee, I always get back to logic. When I was a kid, I missed all the cow patties, but I did catch the one about having enough sense to come in out of the rain.
Thanks for taking the time to keep us up to date!
Keith
Keith,

I do not take kindly to your sarcasm and sadly you show little common sense, much less courtesy. I am tempted to advise exactly how and where you should KISS.

You say, "I originally took the stand that if the alternator on a car doesn't work, just replace it." I agree, but you must ascertain that the alternator is in fact faulty. Your current argument centres on the method of doing so and what you continually suggest, will not find the fault covered here.

Why do you not simply read and understand all of what is involved i.e. a particular and obscure fault? The fact is that the defect being referred to does not always show up as an alternator problem in the normal sense. On the face of it, the alternator works, and as has been reported here can be confirmed OK after the usual test procedures undertaken by professionals. Under these circumstances, you, having common sense and being logical, would not replace it. Logic would have you exploring elsewhere, in a futile effort to put right flashing trouble lights.

This IS the problem and where common sense and logic is required relative to detecting same. I am confident others understand exactly what is involved. I leave silly you with your antagonism.

Trevor. *<(

Edit P.S N.B. Third & fourth posts in this thread:-

http://www.subaru-svx.net/forum/show...ght=alternator
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Last edited by Trevor; 07-30-2007 at 03:22 AM.
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  #27  
Old 07-30-2007, 02:59 AM
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even the arguments on this site are well-written and informative
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  #28  
Old 07-30-2007, 05:20 AM
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Quote:
Originally Posted by AlcyoneDaze
even the arguments on this site are well-written and informative
Pleased it pleases.

How about this, but please read and do not pass over my previous post.

Alternating Orternote

There was once an Svxy naughty sort of alternator, shoving out AC when he shouldn't do so.

Little lights were flashing and he had all and sundry dashing, in glee was he and more so.

They shoved on him a meter, now just what could be sweeter, but it was switched to DC, you see keep it simple was the logic.

Ha ha said the alternator, silly fools are they for sure, my nasty little secret, will find it so easy to just dodge it.

But all was not cut and and dried, and he very nearly cried, reinforcements had arrived, just how now could he cope.

The meter switched to AC and along came a star of screen no less, who had AC for breakfast, his name was Mr. Scope.

Always to remember, when all is asunder, science is the answer with correct decisions made.

Some may say the end is sad, but the twinkling lights were bad, Diode was the villain and AC was his aid.

Trevor.
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  #29  
Old 07-30-2007, 09:01 AM
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And in summation. I had the same problem. I bought a new Alternator. Problem solved.
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  #30  
Old 07-30-2007, 09:39 AM
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Good for you Budbaer!

Quote:
Originally Posted by budbaer
And in summation. I had the same problem. I bought a new Alternator. Problem solved.
Gee Budbaer, You have at least one thing in common. when our alternator is defective, we replace it!
In my case I was able to actually test it in both conditions. Mine was erratic but i caught it in "both acts"
Checked my alternator with my dc voltmeter when all the red lites were on, got 12 volts dc which showed that it was not charging, checked it again with my dc voltmeter when all the red lights went off and got almost 14 volts dc, thought to myself, gee, shouldn't my alternator work all the time? I went to the schematic on the electrical system and determined that all voltage regulators for our cars are built into the alternator itself. replaced the alternator.
Mine now also works great!
Thanks for your input, Budbaer! Now you and I can go on with our lives! (till something else stops working)
Take care
Keith
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