Is it usually only brushes that go out when alternator quits?

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Old 01-20-10, 04:01 PM
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Is it usually only brushes that go out when alternator quits?

Another handy maintenance man/shadetree mechanic told me that(thread title) the other day, when discussing my other neighbors alternator. We had a little powwow in his house, and his wife even brought up some fact that when he was redoing the head gasket on a Dodge like mine, she was putting new brushes in an alternator.

I called up a large auto parts store chain and they said the reman alternator for neighbor's truck will be $130 or 140, depending what amp one he got. And the handy neighbors said you can get brushes kit for like $15(if available). He said he would even do the alternator neighbor's alternator for s**** and giggles!

So I went to tell this to the alternator neighbor, and he did not want any part of it - as he does not trust someone like that. I don't think he believes anybody can so simply fix an alternator. Figuring if it was that simple, then why aren't mechanics doing this, rather than changing them out?????

And he also fears that the handy guy will string things along so that the job does not get done in any timely fashion.
 
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Old 01-20-10, 04:14 PM
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Takes an awful lot of miles to wear out the brushes; how many miles on the beast?

There are a number of things that can fail in the modern alternator.
 
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Old 01-20-10, 04:38 PM
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If it was my vehicle I would be replacing the alternator, end of story. Everything has a usefull life, and when one thing wears out, or malfunctions it is likely that other internal parts are also doing the same thing with a component like this. Perhaps if it were the brushes, replacing them would only buy some short time until something else caused problems like the bearings. Anyway the voltage output failure could also be from a blown out diode for instance that converts AC to DC. In my experience most partial repairs or half done rebuilds on any inexpensive part aren't worth the time, money, or effort, especially when new or fully rebuilt units are not all that expensive, and may even come with some kind of reasonable warranty. Mechanics want and need happy customers also and would not risk leaving their customer with a repair that could easily fail again, perhaps letting them down in a very troublesome or inconvient situation, or at a time when their young daughter was out driving at night. When was the last time you saw a master cylinder rebuild kit? These days we all have high expectations that things will last almost forever, and compared to the past, many things do, but saving pennies on these kinds of low cost failed components will almost always guarantee future work for the The Tow Guy.
 
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Old 01-20-10, 05:24 PM
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Originally Posted by the_tow_guy View Post
Takes an awful lot of miles to wear out the brushes; how many miles on the beast?
Yeah. You'd think the wear on the brushes would be proportionate to the revolutions of it. But am not sure of the possible influence of draw on the alternaror, when perhaps sending more current through the brushes?, as to what that might or might not do.

There are a number of things that can fail in the modern alternator.
Well? So are there on the modern engine. Yet we will spend the money for new plugs and put them in, as opposed to buying a new engine.

I think what it comes down to is how fast one can make such a (partial)repair, and at what cost. Obviously if the shadetree guy did the job for a 6-pack and less than $20 for parts, it might be worth chancing it - to buy more time.

Everything we do, regarding the buying of new or used items and replaing parts in those items has to do with our weighing things out.

If a mechanic were to say charge someone say $110 for simply putting in brushes and charge $200 for a reman, I think most people would probably go the route of the reman, for reasons you and equinox stated.
 
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Old 01-20-10, 06:12 PM
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Like with everything there are always different opinions, and different budgets, but spark plugs are a maintenance item. Alternator brushes are not.
 
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Old 01-20-10, 06:23 PM
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I have a "Unit Repair Manual" for 1992 GM light duty trucks. This is the tear down and service of components like the alternator.

In this book, for servicing the alternator, it says to...

-Clean all metal parts.

-Replace bearings.

-Clean and check...
Brush holder.
Brushes.
Brush springs.
Slip ring end of rotor shaft.
Windings for burned insulation.
Replace rotor or stator if either looks burned.
Terminal connectors for corrosion or breaks.
Windings on stator for chipped insulation.
Slip rings.
Housing for cracks or warping.

-Electrical tests...
Rotor field winding.
Open winding.
Grounded winding.
Short circuit test.
Resistance test.
Stator test.
Rectifier bridge test.
Voltage regulator test.

Then electrical components such as this can experience problems at extreme temperatures. So a final quality check should be done for freezing cold (up north) temperatures as well as very hot (Arizona summer heat) temperatures.

And some alternators will fail only when going fast or with a large electrical load, so a fast speed load test would be a good idea.
 
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Old 01-21-10, 04:15 PM
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Alt

Bushes seldom wear out in an alt. They only carry a small current to excite the alt. unlike a generator where the brushes carried all the current thet the gen. puts out. The reason they are not rebuilt is they are made so as to make rebuilding very difficult. Some of the delcos have the front brng cast into the drive end plate for example.
 
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Old 01-22-10, 02:32 PM
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The thing is though, not only did my neighbor (the shadetree mechanic guy) give me his opinion and experience about the brushes - they also show how to do them in my Haynes manual. So I figured there must be some reason. Reading through the procedure looked relatively easy. Unless they made big changes in design between early 90's vehicles and early 2000 vehciles.
 
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Old 01-22-10, 07:51 PM
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My thoughts on this.. The Garage<> $90 per hour.. re & re alt.. ~1 hour... The Garage to rebuild,, re & re, take it apart, clean it, inspect & test everything with special testers,, put it together & run it up to test 3~4 hours (270~360 labor) plus parts.. Labor alone is worth the reman & lots come with a roadside assistance warranty now.. Lots of ""shadetrees"" out there that try to cheap a repair, than the customer pays in the end,, Sorry Roger
 
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Old 01-23-10, 08:49 AM
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In the past with previous cars I would change the brushes at 100K miles. In my case the brushes and voltage regulator were one unit. In each case, the brushes were about 2/3 worn away. The change was recommended by fellow club members who had far more experience than I.

Regarding bearing wear, some of that comes from belts being too tight. With all my cars I just make them tight enough so there is no squealing on startup. Once the engine warms, the belts tighten because aluminum has a high coefficient of thermal expansion.

If it were my car, I change the brushes. But as I said, I have done this quite a few times so I know it would be done correctly. A COMPLETELY rebuilt alternator is an alternative.
 
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Old 01-23-10, 11:34 AM
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Originally Posted by hopkinsr2 View Post
My thoughts on this.. The Garage<> $90 per hour.. re & re alt.. ~1 hour... The Garage to rebuild,, re & re, take it apart, clean it, inspect & test everything with special testers,, put it together & run it up to test 3~4 hours (270~360 labor) plus parts.. Labor alone is worth the reman & lots come with a roadside assistance warranty now.. Lots of ""shadetrees"" out there that try to cheap a repair, than the customer pays in the end,, Sorry Roger
Why do you have to test run alt. for 3 -4 hours? If you take in your car to a shop, thinking the alt is going out, would the shop test it 3-4 hours? I thought the tests only take minutes. If you take an alt to alt shop, is the guy going to say, "Call me in 3-4 hours and I'll let you know if it is okay or not".?

I guess this all is a classic case of how shade tree guys get to maybe learn more about stuff than the pros. Shadetree guys may even disect parts, where the pro just throws new stuff in, maybe without ever seenig what the inside of parts look like.

I am that way with practically everything I work on. I had a window ac unit all apart this last summer and had the motor out in pieces and relubed the dried-out bearings. Or how I removed a large old fashion bath fan that would have had to have the mount severly changed if new one were bought, and drilled hole in bearing, injected bearing grease, and screwed the hole shut, and the thing now runs as smooth and quiet as new now, after it was a rattle trap before. (Some pro would have come in, tore open the ceiling, put in a new fan, did ceiling repairs, and charged the landlord a bundle.) Did same thing on air handling unit's ac condensor motor, and found exactly what the problem was. Same with taking timers apart, and switches and cleaning up contacts so they work again. BTW -did such a job on a dryer earler last year(or was it even year before maybe?) and it is still good. And the list goes on and on.

So some of these cobble jobs do hold up quite a while, and don't take (at least me) very long to do. You go to the appliance shop and the tech comes out and tells you the customer needs a new appliance because due to their labor rate, it is not worth fixing. The DIY-er can do many of the repairs and make it economically logical.
 
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Old 01-23-10, 11:45 AM
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Originally Posted by LawrenceC View Post
In the past with previous cars I would change the brushes at 100K miles. In my case the brushes and voltage regulator were one unit. In each case, the brushes were about 2/3 worn away. The change was recommended by fellow club members who had far more experience than I.

Regarding bearing wear, some of that comes from belts being too tight. With all my cars I just make them tight enough so there is no squealing on startup. Once the engine warms, the belts tighten because aluminum has a high coefficient of thermal expansion.

If it were my car, I change the brushes. But as I said, I have done this quite a few times so I know it would be done correctly. A COMPLETELY rebuilt alternator is an alternative.
Interesting read. But in your case it still does not sound like there was a failure (yet) as a result of the brushes. Ever find one where the brushes were so worn out that they were no longer working right, and that was the cause of the failure? And by simply redoing the brushes, a lot more life was squeezed out of the alternator before something else on it failed?

.........................................................................

For anyone -

Alternators can go bad from a bad battery requiring the alt to have to charge the bat harder and more constant than normal. What gives out under such circumstances? -overheating of the alt?, causing insulation to burn off the wires? You hear about diodes. Are the diodes normally an issue in alternator failures? I wonder if there is a most likely common failure when the alt goes bad?
 
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Old 01-23-10, 12:44 PM
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Originally Posted by ecman51` View Post

For anyone -

Alternators can go bad from a bad battery requiring the alt to have to charge the bat harder and more constant than normal. What gives out under such circumstances? -overheating of the alt?, causing insulation to burn off the wires? You hear about diodes. Are the diodes normally an issue in alternator failures? I wonder if there is a most likely common failure when the alt goes bad?
In the situation your thinking of, the diodes that make up the rectifier are the weakest link in stock alternators.

I think alot of alternators are damaged simply by incorrect placement of booster cables rather than wear.
 
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Old 01-23-10, 12:58 PM
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You mean like hooking the positive and negative backwards?

BTW - Ford Ranger neighbor said mechanic replaced alt, bat, and serpentine that was all cracked up. Mechanic did not address the clicking. Mechanic said clicking can be stopped by setting control to "floor", rather than "defrost" - and sure enough that stopped it. So neighbor is going to not put it on defrost any more than is necessary to keep from maybe wearing stuff out premature.

Did not ask neighbor what the "damages" were, as I did not want to reopen fresh wounds.
 
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Old 01-23-10, 01:14 PM
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Originally Posted by ecman51` View Post
Interesting read. But in your case it still does not sound like there was a failure (yet) as a result of the brushes. Ever find one where the brushes were so worn out that they were no longer working right, and that was the cause of the failure? And by simply redoing the brushes, a lot more life was squeezed out of the alternator before something else on it failed.
Never had brushes fail on my cars but a friend of mine did on a 70's vintage Dodge or some other Chrysler product. He had the new brushes but did not know what to do with them. I drove him to his abandoned car and installed them for him. The ones that came out were completely gone and alternator was not charging. His idiot light had come on, his battery ran down and engine quit. Someone else advised him about the brushes. This was 1973. I always got to the brush change before any problem occurred.
 
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Old 01-23-10, 02:19 PM
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Originally Posted by ecman51` View Post
You mean like hooking the positive and negative backwards?
No, nothing that obvious. I mean the more common mistake of hooking up battery to battery. If you do the "let's give it a awhile to charge" thing in that setup, the car giving the jump has its alternator open to the demand of two batteries. And one of 'em is drained!
 
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Old 01-23-10, 03:16 PM
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ecman51,, What I ment to say was to properly disassemble & test everything & reassemble & reinstall & retest on the car would be 3~4 hours... Total... I guess I forgot the "about" between the "test" & the "3~4 hours" Sorry about the confusion... Roger
 
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Old 01-25-10, 06:58 PM
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Originally Posted by mickblock View Post
No, nothing that obvious. I mean the more common mistake of hooking up battery to battery. If you do the "let's give it a awhile to charge" thing in that setup, the car giving the jump has its alternator open to the demand of two batteries. And one of 'em is drained!
Could you explain the exact scenarios you are speaking of? For example, you do not say whether the car doing the jumping is running, nor say if the person is leaving the jumpers on if the weak car already got started. And the last sentence and a half (starting at that comma), I'm not sure what you mean. The post is not clear on what type of failure could occur from what given scenario. Sorry.
 
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Old 01-27-10, 08:57 PM
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Smile Alternator Failures & Repairing Approaches

There are three general schools of thought when the "Red Light" comes on:
1. The fix it quick because I have places to go and people to see. They take it to the pro and want it done now, they determine alternator isn't working for what ever reason. The customer doesn't care why, only wants it done in the shortest period of time. They put in a new one and the customer is on their way.
2. The second customer wants it fixed at the lowest cost and wants to know what failed. My experience some of the reasons behind this approach is: Did they really check it and is it really bad. Based on what failed is the cost warranted and/or is it reasonable. Also; based on what has failed do we have it repaired or replaced.
3. The technically savy customer doesn't even consider taken it to the pro until they decide they can't fix it. I personnally fall in this group; after 12 yrs Navy Aircraft electrical maintenance experience, then additional 28 years of computer hardware mfgr / repair and two engineering degrees. We like to think we can fix almost anything; some what like the guys that don't like to stop and ask directions.
 
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Old 01-28-10, 06:49 AM
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As to option 3 above, that is me...

However along with that, is can I get the parts needed?

And if electronic, can I get a schematic (circuit diagram).

Although many times I can fix things without a schematic diagram and can use alternate parts.

But with something which is mostly mechanical like an alternator or starter and on something I depend on like a vehicle, then I think of the terms "preventative maintenance" and reliability.

My preference with both is to get a new alternator or starter. Costs a lot of money, but I live in a rural area and don't want to get stuck out in the middle of nowhere. (Especially in the winter.) There are places around here where cellphones and CB's do not work (mountains/hills).
 
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