M998 60A alternator not charging

[rcamacho]

I’m using the M998A1 component testing and troubleshooting manual. However, this manual refers to the 100 amp alternator versus the 60 amp alternator. Is there any difference in triage?

I’m getting no charging output. I have not yet conducted the amps test however the output voltage is battery voltage currently.

Sent from my iPhone using Tapatalk

 

[rcamacho]

Update:
Per TM 9-2320-280-20-1
Step B2 page 2-204 confirmed voltage on harness side of wire 568. Checking alternator side of wire tomorrow.


Sent from my iPhone using Tapatalk

 

[rcamacho]

Full battery voltage at alternator side of wire 568. Voltage at wire 2A fluctuates in a low range while running.

Moving to removing alternator for disassembly/inspection of voltage regulator and brushes.

Q: is there a bench testing procedure to test the stator windings and other internal components? I’ve not found that in the technical manual.

Sent from my iPhone using Tapatalk

 

[rcamacho]

Editorial this silicone potting is great. A PITA to remove for access to term 568 though.


Sent from my iPhone using Tapatalk

 

[papakb]

Just put your meter lead on the large nut to measure the alternator output voltage. If you only have +24v battery voltage the alternator isn't working. Visit Southern Automotives website, there's a full troubleshooting section there.

 

[rcamacho]

Just put your meter lead on the large nut to measure the alternator output voltage. If you only have +24v battery voltage the alternator isn't working. Visit Southern Automotives website, there's a full troubleshooting section there.

Thanks!
I just happened to find Southern Automotive in the archive and called them today. I did not find their trouble shooting content but hope to speak to them directly tomorrow.

Hopefully this is as simple as replacing the regulator and brushes


Sent from my iPhone using Tapatalk

 

[rcamacho]

Ok, progress.
Removal and disassembly confirms worn brushes. One bush is entirely disconnected from the lead. Ordering a brush kit to repair. Voltage regulator looks good visually.

Q: How are the brushes replaced?
Looks like the rectifier housing needs to be separated from the main body to gain unrestricted access to the brush housing.

Failed brush/disconnected lead

Spade “Sunburst” style voltage regulator

Sent from my iPhone using Tapatalk

 

[rcamacho]

Voltage regulator and rectifier cleaned in preparation for service.


Sent from my iPhone using Tapatalk

 

[rcamacho]

Found TM 9-2920-225-34
Looks like two choices from what I can gather:
1) de solder the rectifier to stator leads and remove rectifier housing
2) remove epoxy vibration potting from yellow capacitor/brush housing to remove brush housing from rectifier

 

[papakb]

The rectifiers can be checked in place with a multimeter. You should have low resistance in one direction on each of the 3 diodes and high resistance with the leads reversed. You should see opposite readings on the other diode block.

The brushes are available for around $10 at most alternator/generator repair shops and after removing the 2 screws holding the brush block in place it should just slip out and the brushes will fall out of it. The new brushes need to be held into the block when it's reinstalled. Make sure the slip rings are clean and not grooved. If they are smooth them out with fine emory paper before putting the new brushes back in. Adjust the block so the brushes ride fairly centered on the slip rings.

Blow everything out with compressed air to remove any carbon dust in the housing.

 

[rcamacho]

Brushes are on the way


Sent from my iPhone using Tapatalk

 

[rcamacho]

Voltage regulator adjustment plug was stripped/frozen. Drilled and extracted so the VR can be adjusted in the future.

10M Tapered plug replacement

Sent from my iPhone using Tapatalk

 

[rcamacho]

Brush holder released from it’s epoxy cocoon. A pencil tip soldering iron worked great in this case.


Sent from my iPhone using Tapatalk

 

[rcamacho]

Slip rings polished up with 400 grit


Sent from my iPhone using Tapatalk

 

[rcamacho]

New brushes installed. Encapsulated Holders/wires/capacitor in silicone to ease replacement in the future if needed.

Sent from my iPhone using Tapatalk

 

[rcamacho]

Done!
The alternator has been reinstalled and adjusted to 28V output per the TM!

Sent from my iPhone using Tapatalk