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Discussion Starter · #1 · (Edited)
This is a guide to disassembling, cleaning, painting, and reassembling the 2.0/2.4L Dart’s 140-amp alternator. These instructions can probably be followed for most modern compact alternators.

Be aware that this is a passion project and will take a great deal of time and effort. I decided to create this guide about halfway through disassembling my alternator having found that there’s very little info on the internet about working on alternators. I sought to put everything I know and learned into one place so that anyone with the time and patience can service their alternator.

140-amp alternator:
Mopar part 56029580AB
Mitsubishi part A2TX3481

120-amp alternator:
Mopar part 56029656AB
Mitsubishi part A002TL0381

My 2013 SE came with the stock 120-amp alternator so I bought the 140-amp from a junkyard on eBay for $60. It worked but looked like crap and I couldn’t stand to leave it in. I didn’t want to pay return shipping on a 15-pound object either so I decided to fix it up.

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For reference here are all purchases I made:

-$60 – the 140-amp alternator from junkyard, ebay

-$80 - New Pulley/overrunning alternator pulley (OAP)/overrunning alternator decoupler (OAD): Litens Part 920032A

-$16 – New bearing, NSK 6303 B17-102DG38 (17mm x 47mm x 14mm), maniacelectricmotors

-$30 - New Terminal block ECU interface/brushes housing, from eBay maniacelectricmotors, part listed as 74033004, but note that the rectifier that they sell has the same part number

-$90 - McMaster-Carr bearing puller 6169K2

-$20 - Sprayon EL609 green insulating varnish, eBay

-$20 - duplicolor paint cans

TOTAL: about $300. The McMaster-Carr puller was an unexpected but necessary expense. Some may be able to get the main bearing off using the table vice method (see “The Rotor and Bearing” section).


A crash course in alternator function

When your engine is running, the crankshaft pulley moves the serpentine belt which in turn spins the alternator shaft via the alternator pulley. Inside the alternator, the rotor (a.k.a. the armature) spins within the stator ring. A magnetic field is created as it spins. The stator carries this alternating current to the rectifier, which converts it into direct current to be sent to the car’s battery. You may have heard of a voltage regulator—Darts’ regulators are contained within the PCM and are not a separate part.

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Removing the alternator from the Dart

Make sure that you disconnect your battery’s negative terminal before beginning.

You’ll first need to remove the engine cover and the air filter box. Then remove the serpentine belt--I take my front passenger wheel out and pull the wheel splash guard over in order to take the belt off. Some may be able to get to it from above without removing the wheel, but for me it's impossible to manipulate the belt that way.

The alternator is held in place by three long screws (13mm socket)—one above and two below. On the back side of the alternator you will have to remove a nut that holds on a wire leading to the battery.


Disassembly

First, remove the four main bolts (8mm socket) holding the two halves of the alternator together. They are in there pretty tightly but don’t sweat it because these are the easy ones.

With those bolts removed, you can now start to separate the housing. Do so carefully because nothing is holding the pulley-side of the housing onto the stator (except perhaps rust, as was the case with mine) and that side contains the heavy part (the rotor). The stator is attached with screws to other side of the aluminum housing (the half with the bolt sticking out of the backside), so do not pull too hard from that direction. First separate the pulley side from the stator ring by holding the stator firmly and using a hammer to gently tap the aluminum corners of the housing (where the 4 main bolts ran through) in order to work it off of the stator. Remember that the rotor is the heavy part of the alternator and it’s attached to the pulley side of the housing.


The Inside

First, dismount the stator from the rectifier by removing the six small screws with a Phillips-head. These are on very tightly so use the largest Phillips that you can and push down hard while unscrewing them. Don’t rush.

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To remove the rectifier and terminal block you have to remove the 2 small screws connecting the rectifier to the terminal block (remove these first), 5 large screws (3 on the rectifier, 2 on the terminal block), and the single nut on the screw sticking through the back of the housing (attached to the rectifier). The same rule applies—be extremely firm and use a large Phillips head. I stripped one of the 5 big screws and had to use a small rotary blade to cut a new flathead-shaped groove in it (pictured below).

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The nut on the bolt sticking from the back of the housing requires a 12mm socket. I had to break off the sides of the black plastic piece to get at it. I could not find a replacement for this plastic piece, so I kept the main part to put back on during reassembly. You will also remove a hollow metal cylindrical piece from underneath the black plastic part during this step.

Now you’ve disassembled half of the alternator. To remove the rotor, you’ll need to remove the pulley.


The Pulley

The pulley cap alone is difficult to remove and you should assume that you will have to break it by stabbing a screw driver through the center. The new pulley that I purchased came with a cap.

Two sets of instructions came with the new pulley—one describing how to remove it with an impact wrench (along with the 17mm hex tool included with the new pulley), and one to remove it with specialized tools. I spent quite a lot of time searching for specialized tools for our alternator—beginning with the Litens website—and there aren’t any out there. To be able to use special tools, the inner hole (inside the pulley hex hole) needs to be another smaller hex key. Our alternators just have a round hole in there, so they require the impact wrench method. I went to an alternator shop to get advice on getting it off. To remove it, you hold the pulley in your left hand, and give the impact gun one hammer. It should come off easily.

NOTE: Do not use a hammer on the pulley shaft to bang it out of the housing. It is soft metal.


The Rotor and Bearing

Note that there are 2 bearings: the main/front bearing between the rotor and the pulley, and the rear one that is exposed on the opposite end of the shaft. I read somewhere that the rear bearing usually doesn’t need to be changed, and so I didn’t change it. I will be referring to the main bearing for the rest of the guide.

With the pulley off you now need to separate the rotor from the housing, assuming that you want to change the bearing and clean the rotor like I did. The four Phillips screws around the pulley connect to a retainer plate that holds the bearing on. You’ll need to remove them first. It may be very difficult—I had to grind 3 of them into flathead style. They are M5-0.8 x 15mm screws. I could only find 14mm and 16mm length, so I bought 16mm screws. I installed them and they fit.

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After removing those four screws, you’ll probably find that the rotor still won’t come out since the bearing has seized onto the housing. I used a 4” PVC pipe (which the rotor fits neatly into) to hit on the ground. Make sure to stuff a big towel inside for when the rotor falls out!

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Now you’ve removed the rotor.

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Alas, you still have another problem to deal with here because the bearing has also seized onto the rotor shaft. There are youtube videos where people crush the bearing with a table vice and then grind off the inner ring (see this video: https://www.youtube.com/watch?v=sTTfemu_gcY). I instead paid $90 for a nice bearing puller from McMaster-Carr (part 6169K2; see parts list at top). I tried to crush the bearing with my table vice but mine is not strong enough. If you can remove the bearing that way then you’ll save money assuming you already have the tools.

All pullers available at local auto shops, etc did not fit under the bearing. Only 1/8” jaw tips will fit.

I also discovered a spacer ring under the bearing plate when the bearing came off.

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The main bearing is NSK, B17-102DG3. It is a 17 ID x 47 OD x 14 W bearing. I bought NSK part B17-102DG36 to replace it. It is identical.

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Discussion Starter · #2 · (Edited)
Cleaning

For the aluminum housing and the exterior of the stator ring I used a 3-inch wire wheel on a handheld drill. Obviously it’s not necessary to clean the housing. To get into small spaces, I used 5mm wire brushes that I purchased off eBay. I didn’t get every little bit. These small brushes are useful for cleaning the rotor. If you have access to sand/glass bead blasting then that’s a great way to clean the housing.

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The old paint on the outside of the stator ring can be easily wire brushed off, but it will have to be repainted so this is not necessary if you aren’t concerned with appearance. I did not do anything to the inside of the stator ring.

For the rotor I used all 3 types of wire brushes. The small ones wear out quickly so I just started to jam them in tight spaces to get rust off—it works more or less. I did not get 100% of the rust off—my goal was just to get all the clumpy/bumpy rust off so that I had as smooth a surface to paint as possible. Some of the previously rusty surfaces (such as the backsides of the rotor pads) are still a bit orange, but smoothed out from jamming the little wire brushes back there.

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Painting

Stator: I used Low-gloss black Duplicolor engine paint (500 degrees). I used this to paint the bearing retainer plate as well.

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Rotor: To paint the rotor, I used Sprayon EL609 green insulating varnish (EL601 red insulating varnish is fine to use too). Make sure to first get as much rust off of the rotor as you can. Use care when using this product—it is highly toxic (“suspected of causing cancer”). Instructions are on Sprayon’s website. After painting, don’t let the rotor sit on its side for more than a few minutes—it’s so heavy that even dry paint will stick to the surface it’s sitting on. Store it sideways, with both ends of the rotor shaft resting on raised objects.

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I learned about insulating varnish through these two threads:
-How do you clean an alternator?
-Bosch alternator varnish / paint experts required! - PeachParts Mercedes-Benz Forum.

Housing: I used Duplicolor 500 glossy black. I stuffed aluminum foil into the bearing wells so they would not get painted.


The Terminal Block and Brushes

I bought a new terminal block on eBay (refer to the parts list). I did so mostly because it came with new screws which I needed. Below is a picture of the old brushes (with 46k miles) next to the new ones. I probably could have left the old ones in.

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The new terminal block came with a thin pin to hold the brushes in until you re-insert the pulley shaft during reassembly. If you’re reusing your original terminal block, use a paperclip to hold the brushes in. There is a small hole in the alternator’s housing through which you run the pin or paperclip to the outside for removal after reassembly.

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Reassembly

Connect the rectifier to the housing with its 3 large screws (and their plastic washers). Then set the terminal block in its place (running the pin or paperclip through the small hole to hold the brushes back), taking care to properly seat the black rubber seal between the terminal block and the housing. Install the 2 large screws into the terminal block.

Next, connect the terminal block and rectifier using the two small screws that sit on either side of the brushes. Now you can tighten these 7 screws.

On the back side with the protruding screw, insert that metal cylinder into the hole with the screw. Then sit the black plastic piece on top and tighten down the nut. It doesn’t need to be too tight or you can break the plastic piece.

Place the stator into the housing. Make sure that the ring is set evenly all around. The windings should fit snugly into their respective places in the rectifier. Tighten those 6 screws.

Bearing: For the rotor’s half of the alternator, you’ll first need to install your new front bearing. Rub a dab of oil around the outside of the bearing and put it in its slot in the housing. Attach the bearing retainer bracket using the four screw holes around the center.

Remember to place that little spacer ring on the rotor shaft so that it sits between the bearing and the rotor.

With the spacer on the rotor shaft, insert the rotor shaft through the bearing and push it firmly in all the way. Next, the pulley will be installed. The Litens pulley I bought came with instructions (as I mentioned before, the “alternate” instructions are what our alternators need). Screw the pulley on by hand as far as possible. Next, take the included 17mm tool and place it into the pulley slot. Use an impact gun and give it 2 or 3 hammers while holding the outer ring of the pulley in your other hand. Afterward, ensure you’ve tightened it enough by using a hand tool to try to loosen it.

You can put the pulley cap back in now, but I waited until the alternator was fully assembled to install it.

Now you can put the two halves together. Don’t try to rotate the rotor/pulley until it’s fully seated—the rotor is supposed to barely fit and until they’re completely together it will not be able to spin without scraping the stator.

Once the stator is firmly set into both halves, you can install the 4 main housing screws, their heads on the pulley side of the alternator. Finally, pull out the pin that was holding the brushes in.

If you installed new brushes then you’ll need to break them in. When I first hooked up the alternator it didn’t work! After some anxious pondering I searched and found this page (Automotive Alternator Break-In Instructions). Basically, you need to run the car (in park/neutral) for about 10 minutes just above idle and then take a 15-minute break. Repeat this until you get a reading of around 14V while the engine is on.

Multimeter use: When the engine is turned off, your battery should read around 12.5V on the multimeter (touch each contact to the respective battery terminals). When the engine is on and your alternator is functioning, it should read around 14V. If the alternator is not working then it will read 12V or lower.

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