Repairing my original factory 1973 alternator, how hard is it?

[bennydodge]

Well, the factory alternator on my '73 Challenger is no longer charging/outputting. I would like to retain it, as it's the original to the car, so I will be rebuilding or restoring. I do have a factory service manual. Any tips or pitfalls before I start disassembly?

 

[pschlosser]

find a rebuild kit. there are 6? diodes in there *rectifier) that eventually go bad. but it's not just the electrics, it may be a good time to replace bearings, as well. there are service providers you can send it to to have that specific one rebuilt.

 

[bennydodge]

I'm thinking rebuild kit as well. I guess after 53 years it could stand to be restored. it doesn't look too bad but it does make a clicking noise when the pulley is turned, not sure if that's normal.

 

[gran coupe john]

I used to rebuild those alts. In the late 70s. The noise is most likely a front, or rear bearing. Change the brushes, and clean the armature with emery. Should run like new.

 

[Challenger RTA]

The above information is good. I take it you look to at the date code on the alternator. I have seen were the alternator has been condemned and it's the grounds. Mounting bolts and cables. With it making a noise it's needs a look it as said above.

CHRYSLER ALTERNATOR PARTS (early)

 

[larry4406]

Should you decide to rebuild it, continue the thread so we can all see how its done!

 

[Vaanth]

Well, the factory alternator on my '73 Challenger is no longer charging/outputting. I would like to retain it, as it's the original to the car, so I will be rebuilding or restoring. I do have a factory service manual. Any tips or pitfalls before I start disassembly?

Repairing, or rebuilding, a 1973 Chrysler alternator is relatively straightforward, particularly if it is in unmolested original condition. The 1972 - 1977 version is the second type of the "Isolated Field" design, commonly called the "square back" due to the shape of the rectifier openings on the rear end shield, or case. It is simpler to repair or rebuild than the earlier alternators: 1960 - 1969 "Grounded Brush" type, 1969 "Insulated Brush" type, or 1970 - 1971 "Isolated Field" type. The earlier type are commonly called "round back" due to the appearance of the the rear end shield, or case, compared to the square back. The square back type was revised in 1978, and used through 1987. The later revised version shares some parts.

The 1972 - 1977 version uses bolt-in rectifier, or diode, "trios" including the attachment of the stator. The earlier versions used pressed-in individual diodes, with soldered connections for the diodes and stator windings. Other than these differences, most of the repair or rebuild is similar.

Individual parts are available, as are rebuild kits. Bearings are typically sold separately. Parts and kits are available from several sources including Quick Start, such as the Square Back Repair Kit. Valley Forge has repair parts including major components as well as new end shields for some alternators. They are really a supplier to rebuilders mostly and sell in bulk. See Chrysler Alternator Parts. Parts such as brushes, bearings, etc. are typically available at parts stores.

Before removal of your alternator, disconnect the field terminals, and check resistance between the two terminals with an ohm meter. If the resistance is open or much higher than about 5 ohms, it is likely a brush problem. Badly work brushes and/or worn/broken brush holders, or a damaged slip ring, can lead to a clicking or rubbing noise in addition to failure of the alternator to charge. The brushes can usually be removed with the alternator installed. Remove the brushes for inspection. Crank the engine and if the noise is gone, the brushes/holders/slip rings are the culprit. If the brushes are worn or broken, replace them. If the surfaces are gouged badly, the slip rings may be bad. They can partially be seen, but alternator disassembly is required for full inspection or replacement. If not gouged or badly worn, the slip ring surface can be cleaned and refinished with fine sandpaper. If the slip ring assembly requires replacement, desoldering and soldering of the connections is required.

The next likely causes are possible debris in the alternator or something separating from the rotor/stator, the front bearing, or rear bearing. The front bearing wear more before the rear bearing usually.

An alternator pulley puller is needed to remove the pulley and front bearing/end shield. A specific puller is available for the Chrysler pulleys and works better than universal types. A press is required to remove and install the rear bearing, install a slip ring, and to install the front bearing a pulley. It can be done without a press, but the press makes it simple. When pressing, support the rotor, not the end shield. The service manual details the troubleshooting, disassembly, repair, and assembly operations.

The following image shows a basic repair kit:

The following image shows the brushes:

The following image shows the diode trios and capacitor:

The following image shows the slip rings:

The following image shows the rear and front bearings:

The following image shows the rotor:

The following image shows the stator installed in the rear end shield:

For comparison to the simple bolt-in diode trios, the following image shows the earlier individual press in and solder diodes:

I've rebuilt many alternators and starters over the years. It is best to start with one that has not gone through the mass rebuilder process using poor or mismatched parts in ruined blasted housings. With one exception, I have not had to rework any that I have rebuilt and ran over the last 50+ years, but for projects or if needed, I keep a few alternators that I have rebuilt on the shelf:

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[Vaanth]

Repairing, or rebuilding, a 1973 Chrysler alternator is relatively straightforward, particularly if it is in unmolested original condition. The 1972 - 1977 version is the second type of the "Isolated Field" design, commonly called the "square back" due to the shape of the rectifier openings on the rear end shield, or case. It is simpler to repair or rebuild than the earlier alternators: 1960 - 1969 "Grounded Brush" type, 1969 "Insulated Brush" type, or 1970 - 1971 "Isolated Field" type. The earlier type are commonly called "round back" due to the appearance of the the rear end shield, or case, compared to the square back. The square back type was revised in 1978, and used through 1987. The later revised version shares some parts.

The 1972 - 1977 version uses bolt-in rectifier, or diode, "trios" including the attachment of the stator. The earlier versions used pressed-in individual diodes, with soldered connections for the diodes and stator windings. Other than these differences, most of the repair or rebuild is similar.

Individual parts are available, as are rebuild kits. Bearings are typically sold separately. Parts and kits are available from several sources including Quick Start, such as the Square Back Repair Kit. Valley Forge has repair parts including major components as well as new end shields for some alternators. They are really a supplier to rebuilders mostly and sell in bulk. See Chrysler Alternator Parts. Parts such as brushes, bearings, etc. are typically available at parts stores.

Before removal of your alternator, disconnect the field terminals, and check resistance between the two terminals with an ohm meter. If the resistance is open or much higher than about 5 ohms, it is likely a brush problem. Badly work brushes and/or worn/broken brush holders, or a damaged slip ring, can lead to a clicking or rubbing noise in addition to failure of the alternator to charge. The brushes can usually be removed with the alternator installed. Remove the brushes for inspection. Crank the engine and if the noise is gone, the brushes/holders/slip rings are the culprit. If the brushes are worn or broken, replace them. If the surfaces are gouged badly, the slip rings may be bad. They can partially be seen, but alternator disassembly is required for full inspection or replacement. If the slip ring assembly requires replacement, desoldering and soldering of the connections is required.

The next likely causes are possible debris in the alternator of separating from the rotor/stator, the front bearing, or rear bearing. The front bearing wear more before the rear bearing usually.

An alternator pulley puller is needed to remove the pulley and front bearing/end shield. A specific puller is available for the Chrysler pulleys and works better than universal types. A press is required to remove and install the rear bearing, install a slip ring, and to install the front bearing a pulley. It can be done without a press, but the press makes it simple. When pressing, support the rotor, not the end shield. The service manual details the troubleshooting, disassembly, repair, and assembly operations.

The following image shows a basic repair kit:
View attachment 158144

The following image shows the brushes:
View attachment 158145

The following image shows the diode trios and capacitor:
View attachment 158147

The following image shows the slip rings:
View attachment 158149

The following image shows the rear and front bearings:
View attachment 158146

The following image shows the rotor:
View attachment 158148

The following image shows the stator installed in the rear end shield:
View attachment 158143

For comparison to the simple bolt-in diode trios, the following image shows the earlier individual press in and solder diodes:
View attachment 158150

I've rebuilt many alternators and starters over the years. It is best to start with one that has not gone through the mass rebuilder process using poor or mismatched parts in ruined blasted housings. With one exception, I have not had to rework any that I have rebuilt and ran over the last 50+ years, but for projects or if needed, I keep a few alternators that I have rebuilt on the shelf:
View attachment 158151

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To add to my post, the following outlines some bearing installation details from a post of mine on For FMJ-bodies Only about a question as to how far to press the rear bearing into the end shield.


Placement of the rear bearing in the end shield:

For the drive, or front, end shield (aka. case half), the bearing in the end shield recess and press in until it bottoms. Install the retainer. Then, supporting the rotor back end, align the bearing/end shield,and using a sleeve that fits around the shaft and on the bearing inner face (or Chrysler tool C-3858), press the bearing down on the shaft until it bottoms. The collar on the rotor shaft limits and places the bearing correctly.

To install the rear bearing properly in the rear, or rectifier, end shield use Chrysler tool C-4201 (parts C-4201-1 and C-4201-2). Position the rectifier end shield bearing on base of tool C-4201 (C-4201-1). Place the rear end shield on top of the bearing aligning it to press evenly. Use the other part of tool C-4201 (C-4201-2) on end shield, and press it into place until it bottoms. The lower part of the tool limits and places the bearing correctly.

Without the Chrysler tool, support the rear, or rectifier, end shield around the bearing area with an open sleeve or similar. Align the bearing in the opening to press in evenly. Using a cylindrical block slightly smaller in diameter than the bearing press in until the bearing is as follows:

- For an aftermarket smooth bearing, in a 1972 -1977 alternator, press until the surface of the bearing is slightly above the surface of the end shield.

- For an original ribbed bearing, in a 1972 -1977 alternator, press until the surface of the bearing is slightly higher above the surface of the end shield than a smooth bearing.

- For an aftermarket smooth bearing, in a 1978 -1987 alternator, press until the edge surface of the bearing is slightly more than 1/8" below the surface of the end shield.

- For an original ribbed bearing, in a 1978 -1987 alternator, press until the edge surface of the bearing is about 1/8" below the surface of the end shield.

NOTE: Describing the depth of the surface in relation to the shield surface is a little difficult to do quantitatively, but after doing a few, one gets a feel for it. Depending on component variances and possible manufacturer depth difference, the depth can vary.

NOTE:Adjustment may be required if binding occurs when the unit is assembled. Before tightening the shield mating bolts fully, or installing brushes, spin the rotor and feel and listen for roughness and binding. If detected, disassemble, and press the rear bearing back slightly, until the rotor spins freely.

NOTE: If using the bearing grease shield on the slip ring end of the rotor, slightly more clearance may be required to prevent rubbing of the shield on the bearing.

Following are a few images of alternators I have done for reference:

1972-1977 with smooth bearing. Bearing surface slightly above shield.

1972-1977 with smooth bearing. Bearing surface even with shield surface.

1978-1987 with ribbed bearing. Bearing surface edge ~1/8" below the shield surface.

NOS 1978-1987 with ribbed bearing. Bearing surface edge ~1/8" below the shield surface. This bearing has never been out, but I did disassemble the alternator to inspect and change the pulley.

I didn't have an earlier alternator with the ribbed bearing handy to show.

Installing the bearings using a press:

Installing rear bearing:

"Tools" used with the press:

Installing front bearing with a sleeve:

"Tools" used with the press:

If a sleeve that fits in the end shield opening and over the rotor shaft is not available, something that fits around the shield opening a bears on the bearing area can be used with some caution to not stress the aluminum and bearing too much:

"Tools" used with the press:

For the sleeve, I used an old 9-1/4" axle crush sleeve stacked with an S-2 outer bearing race.

A press makes this relatively easy, but if one is not available, threaded rod and nuts/washers could be used for the front bearing. Both could be done with sleeves and blocks and a hammer if working slowly and carefully.

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