Alternator Rebuild - How to

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Alternator Rebuild –Write-up:

Disclaimer: What you read or observe here is by NO MEANS the ONLY or BEST way of accomplishing the underlying task. These are procedures that have worked for me and in no way do I take responsibility for any damage that may become of you or your personal property. This write-up is solely for reference of your own research and knowledge.


Vehicle: 1995 Mazda Millenia 2.5L (May apply to other years)
Prior to deciding to rebuild my alternator my car had a hard time keeping my battery charged. I suspected that my alternator was about to eat it. I put it on a bench test and saw that it was putting out ~13.4Volts and a meager ~18-19 amps total. The oem configuration calls for at least 14.5 volts at 110amps.

I will omit the removal procedure because that is a write-up on its own. When I started this project out I assumed it would have taken me an hour or so tops because I figured I could have pulled the alternator out from the top of the engine. After consulting the manual I found out that the AC compressor had to be unbolted and swung away to make room to drop the alternator from below. Furthermore, I had to drop the engine down a few inches on the passenger side to clear the lower alternator bolt. I was not able to just wiggle it free and had to remove the bolt entirely.

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Parts List:





<strike>Transpo/WAI IN441 Voltage regulator</strike>
<strike>Transpo/WAI INR733P (see note below)</strike>
Timken 201DD Bearing (see note below) or Mc Master # 5972k55
Timken 303DD Bearing (see note below) or Mc Master # 2349k621





Transpo/WAI 39-8203 Brush holder


Assorted sockets, wrenches, extensions, shop press.
Electric contact cleaner (see note)

The above parts were quite difficult to find. Transpo/WAI is a large OEM supplier that really only sells in large bulk to rebuilders and persons with special accounts. Obtaining these parts “cheaply” will dictate if it is more economical to buy an already remanufactured alternator or to buy the parts yourself. Although the parts can be had on ebay (various manufactures) from time to time; they are far too costly to buy individual pieces rather than a whole new remanufactured alternator with warranty. The re-sellers of these parts mark these up so greatly to cover their bulk overhead. I was fortunate to use my company’s account to purchase some remaining stock one supplier had in hopes to start rebuilding hi-output alternators on my spare time. The OEM rectifier <strike>(INR733)</strike> is listed at 110 amps. The <strike>(INR733P)[s/] is a NEW updated “heavy duty rectifier” and in conjunction with the matching [s]IN441</strike> voltage regulator performance was astronomical. I will elaborate on this later on.

Bearings: The listed bearings for my application on the Timken site were wrong. When my bearings arrived they were both too small. I don’t know the proper bearing size as various sources called for the same size. I do not know if my alternator was just a freak or if there is something special about it. I will leave the part numbers up as a reference for others that might find it useful. I was fortunate that the bearings in my alternator were holding up very well so they were re-used.

Note* DO NOT USE CARB/BRAKE CLEANER ON THE STATOR WINDINGS!!! Make sure and get some electrical contact cleaner.

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The first step once you have the alternator in your hand is to remove the pulley. I don’t recommend doing this any other way than using a good impact gun. I have tried clamping the pulley in a vise in the past have almost always ended up buggering up the pulley. Notice I soaked the nut well with PB blaster.

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This is the rear of the alternator. There is a minor heat shield not shown. I removed it while the alternator was still on the car. There is a small wiring clip attached to it and I did not want to risk breaking the clip so I just removed the shield and clip together and left it on the car. There are 4 bolts that need to be removed for the rear shield to come off.


The battery terminal will need to be removed first to get the shield off.


Once the battery terminal is removed carefully pry the rear shield off exposing the components.

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Rear shield removed.

The new rectifier is an 8 diode heavy duty type with 4 stator contact points. (see comparison below) I used an impact screwdriver to remove the screws as to not strip any.

Another view.

The brush holder assembly is removed with two screws.

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Notice how worn my old brushes were. 90% of the time you are good with just swapping these out and cleaning the slip ring contact points.

Voltage regulator and brush holder are removed in this picture.

Old voltage regulator.

Old rectifier is removed.

Rectifier

All old parts removed.

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Slip ring. (Sorry for the blurry pic) Notice glazing of contact points.

With the pulley off and the internals stripped the two halves can be separated. Carefully work your way around. Do not stick a screwdriver in there trying to pry them apart. The windings are very fragile and if you nick the insulating varnish coating you’re going to arc your windings and this whole process would be useless.

Internals of Alternator housing.

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It wasn’t until this step that I realized I had the wrong bearings. The rotor was gently pressed out of the housing on my shop press revealing the rear end bearing. The bearing has a plate with 4 screws on it that need to be removed as well to access it.

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Rotor removed.

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Alternator parts after a mild acid wash and electrical contact cleaner on the windings. I used a soft toothbrush and a good amount of contact cleaner on the windings. I flushed and flushed until the runoff was clean.

This is probably one of the most important steps to the whole process. You must clean up the slip rings to make sure you get good electrical contact between the brushes and windings. I used a scotch bright type of sanding pad. It was soft enough to polish but not too aggressive.

This is where things really come to shine. Here is the comparison of the old rectifier and the new “heavy duty” Hi amp one. You can clearly see the beefier build and greater heat sink. Some of the diodes on my old one seemed to be fried as well and contributed to my low amperage output.