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Homebrew alternator rebuild

jimmydaux

jimmydaux

NAXJA Forum User
Location
Centerville, Utah
I went and played in the mud last night for a bit, and when I got done my dash started yelling at me to check guages. Voltage was down t 9 volts and belt was fine, so I pulled the alternator to check things out. It was pretty dirty so I cleaned it out pretty good. There were some pretty deep groves where the brushes ride on the two contact points on the the armature (I think thats what its called). Between the grooves and brushes that only extend out a little tiny bit, there didnt seem to be much if any contact. I turned the contact points down a bit on the lathe, and then machined a sleeve to slip over the existing slip rings to increase the diameter a bit so it would contact the brushes better. Putting it all back together like this bumped my voltage back up to 14.

My only issue now is that I dont have much brush life left over. Does anyone have or know where I can get a new or more fresh set of brushes for a denso alternator? I found one place online that sells them for $20, but Im hoping to find a better answer than that.

Also, does anyone know what is done internally to an alternator to make it a "high amp" alternator? My local alternator shop says they can convert it, but Im just curious if I can do it myself. Anyone proficient in the art of alternator modification?

Jeremy
 
An alternator shop should be able to rebuild it and rewind it for more amps. If they say they can't what the hell do they do? Get junkyard altnerators, spray some break cleaner on them, then resell them as rebuilt? lol!
 
Check your alternator shop for parts. I got bearings for my denso alternator there a few years ago.
 
The contact points you refer to are known as "slip rings" - just FYI (if they're segmented, like they are on starter motor armatures, then they're "commutators" or "comm rings".)

The primary difference between a "standard" and a "high output" alternator is the windings on the armature - the higher-output version will use a lighter-gage wire so that more current may be generated (by dint of having more windings travelling through the magnetic field. High-output ignition coils are done much the same way - the secondary windings use a finer wire = more coils affected by the collapse of the magnetic field = higher output current = greater spark energy.)

Fine-wire/high-winding-count armatures aren't common parts - which is why most small shops will only go so far with upwinding alternators (since they can only get armatures wound with so fine a wire.) Mean Green, Powermaster, et al actually have to wind their own armatures to get the power levels they produce.

Also, the rectifier diodes in the back of the alternator have to be heatsunk to a much greater degree - the more current a diode is rated for, the more power it handles. Rectification of high-current AC yields great heat - without proper heatsinking, your diodes are going to melt themselves down.

The regulator typically wants to be beefed up a little bit, but it doesn't need much. The field coils are essentially the same between standard and high-amp units - for the most part. There are some "specialty field coil assemblies" out there as well. However, the reverse tends to apply - they use a larger wire, since a larger wire has greater ampacity = more current-handling ability = greater magnetic field strength = greater effect on the armature windings.

If your local shop sez they can't upwind your alternator, find a new shop. They should be able to make it happen with parts that are commonly available. Maybe not push it to 200A or more - but there's no reason that most alternators can't be upwound with OTS parts (unless they're already at the peak output level that can be provided using standard OTS parts, and not having to get anything purpose-build or one-offed.)
 
5-90 said:
The contact points you refer to are known as "slip rings" - just FYI (if they're segmented, like they are on starter motor armatures, then they're "commutators" or "comm rings".)
I turned down the originals so they were the same size and concentric, pressed the new sleeve on and used a splitting tool to sepparate the two rings. Its worked like a charm so far.

5-90, you seem like you know a bunch about this subject, any pointers on how to refresh the brushes without entering the just buy a new part realm? Is it possible to remove the brushes from the holder on the delco alternator and replace just the brushes, rather than the brush holder assembly as a whole?
Click to expand...
Click to expand...
 
jimmydaux said:
5-90 said:
The contact points you refer to are known as "slip rings" - just FYI (if they're segmented, like they are on starter motor armatures, then they're "commutators" or "comm rings".)
I turned down the originals so they were the same size and concentric, pressed the new sleeve on and used a splitting tool to sepparate the two rings. Its worked like a charm so far.

5-90, you seem like you know a bunch about this subject, any pointers on how to refresh the brushes without entering the just buy a new part realm? Is it possible to remove the brushes from the holder on the delco alternator and replace just the brushes, rather than the brush holder assembly as a whole?
Click to expand...

You can find just the brushes and springs (at last recall,) but it would take some looking.

For a "quick hit" to clean up the brushes, sand the business end down with an emery board. Back it up with something hard. Try to file the ends flat and clean them up - they'll take shape again soon, and you'll be making contact on a fresh surface.

(Yeah, I know plenty. I used to get my arse chewed for rebuilding them right on the parts counter at Kragen's when a customer needed a replacement and we didn't have one on the shelf, but we had parts...)
Click to expand...
Click to expand...
 
how fast do the brushes wear? It took a minute or so of running to get the voltage up to par, I bet that was when the brushes wore into the new diameter of the slip rings. I bet I only have 1/16th of an inch of brush extension left until there is no spring pressure pushing the brushes against the slip rings. Any guess on how long that would last?
 
A brush is essentially compressed graphite (it's called a "brush" because that's what it used to be - a fibrous brush. They decided some time ago that compressed graphite was easier to work, handle, and install.)

I'd probably just get a new set - they're usually cheap enough. I know you used to be able to get them easily enough as just bare brushes - no holder assembly - but I'm not sure if that's still doable. Probably is, you just might have to look.

Since they're compressed graphite, I'd not expect them to run for a great deal of time if they're getting short. Also, the brushes aren't likely to actualy extend all the way out of the holder - the springs themselves are relatively weak, and you don't want the thing to just jam on you all at once, right?

Just don't forget your toothpick for when you put it all back together!
 
Well luckily I was able to find a new brush holder for about $10 bucks. I got it all put in today. After looking at it after I pulled the alternator for the second time, I think I could have done it fairly easily without pulling the alternator.

So, if your alternator starts giving you fits after mud, youve probably got worn brushes or slip rings. Ive read that a lot of time the mud can even just keep the brushes from extending properly which prevents contact with the slip rings.

These are the rings that I pressed on. I pressed a single sleeve then cut it in half to separate the two contact points. Make sure you measure first where the cut needs to be. If you dont, the cut is just guess work. I was amazed at how long the new brushes were. All in all, this saved me over $100 dollars. It runs great and charges like new. My only cost was time ant $10 dollars for the new brush holder assembly. Im willing to bet that for the most part, you should be able to get an alternator running again after water/mud by pulling it apart, cleaning it, and making sure that there is proper brush contact and pressure, replacing the brush holder unit if necessary.

DSC07699.jpg


DSC07700.jpg


DSC07701.jpg
 
I bought it from a local shop called action alternator and starter. He knew right what it was and didnt even need to look up a part number. If you need one and cant find one local I can easily pick one up and ship it to you. It would be about $15 with shipping and such.
 
Jimmy, When you initally had the low reading and check engin light come on did you check everthing out with a volt meter?

I ask because I had the same thing happen to me lastnight when driving home and I assumed my alternator just pooped out on me. Before I shut down the engin I pulled out the volt meter and and found that it was actually putting out excess power (17.8-18 volt range) but the dash gauge indicated 9 volts. Then I shut it down my battery was reading slightly high (13.5 range). When I tried to restart it the motor fired right up and the check engin light was off and the dash meter was reading 14 volts again.

As of this morning everthing is as it should be...

Does anyone know if there is a voltage regulator of some sort? or is the alternator disigned to put out 14 volts no more no less?
 
every alternator has to have a voltage regulator. Check your battery connections, sounds like you've got a bad one. The clamps act as a resistor, the gauge will show that, and the alt. will try and make up for it by pumping out more power.
 
I did check it with a volt meter. I dont recal the exact reading. When I turned it off and started it back up again it seemed normal for a bit but then dropped off again. After replacing the brushes and slip rings theres been no issues whatsoever and tested voltage is 13.xx volts.
 
Bear in mind that the "voltage regulator" for an alternator is actually used and intended as a current output regulator - cf: Ohm's Law.

Sounds roundabout, but it actually does work. When resistance increases, current will decrease unless voltage is increased - so the "voltage regulator" actually increases current output to maintain nominal output voltage - at least, up to the maximum output potential of the alternator (which can vary from "rated max" by as much as -5%/+10%.)

Voltage regulators also used to be adjustable (before they became solid-state,) now we're stuck with 13.5-14.0VDC as a nominal operating voltage - not necessarily a bad thing, but it's a change from before.
 
i just rebuilt my alternator and i noyiced i found some for 3 dollars a set but no brush holder then i found em with a brush holder for 30 bucks sama as a whole alt from the junk yard ,,,but are all brushes the same i found toyota one's for 3 where honda runs for 26 dollars it makes no sense can i squeeze toyata model brushes in i got a dremel tool so i supose i could shave down what dont fit but they look like they do i just unsoldered the old brushes out and kept the springs all i need is to put the new brushes in and its a denso alternator that im working on any sugestions and ebay and parts geek got the cheapest at 3 dollars a pair ???
 
attemptmischief said:
i just rebuilt my alternator and i noyiced i found some for 3 dollars a set but no brush holder then i found em with a brush holder for 30 bucks sama as a whole alt from the junk yard ,,,but are all brushes the same i found toyota one's for 3 where honda runs for 26 dollars it makes no sense can i squeeze toyata model brushes in i got a dremel tool so i supose i could shave down what dont fit but they look like they do i just unsoldered the old brushes out and kept the springs all i need is to put the new brushes in and its a denso alternator that im working on any sugestions and ebay and parts geek got the cheapest at 3 dollars a pair ???
Click to expand...
please use periods (.) to seperate your sentences so that they are easier to understand. as for using brushes from a different manufacurer i dont think that will work. the brush width, thickness, and height all need to be the same, plus the way that they "attach"
 
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