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M939 200 amp alternator upgrade

jetjockB747

Member
62
3
18
Location
Palmetto Bay/ Fl
After installing an RD AC unit on my truck, the stock 60 amp alternator has fallen short on amperage. The solution, a bigger alternator.
I have recently acquired a Neihoff 14/28V 200 amp alternator to feed the electrical system on my M923A2. Does anyone know what and if, any electrical modifications will need to be made? Installation ideas and such?
I am upgrading from the stock 60 amp 28V alternator.
The alternator in question is a Neihoff model N1228 with external regulator N3123. This thing is massive.
:grd:
 

74M35A2

Well-known member
4,145
326
83
Location
Livonia, MI
The alternator B+ output lead usually goes directly to the starter B+ lead. Besides wiring the external regulator correctly, only other item would be to check and possibly upgrade the charging wire from the alternator to the starter, whatever size is rated for 200A. Look it up and compare to what you have. It should he relatively short, and most welding supply shops carry nice fine strand copper cable sold by the foot in any gauge, with heavy duty copper lugs also.

The battery cable from the batteries to the starter can handle it, since they carry starter current already.
 

jetjockB747

Member
62
3
18
Location
Palmetto Bay/ Fl
Yes I did. The external regulator is mounted on top of the alternator and wired to it. It turns out the alternator in question is for a HEMTT. Too large for the M939. It has been returned.
On a side note, I did find two of my Hawker batteries were at 11.5V. I have since removed them, and are currently running a two battery configuration. The stock 60 amp alternator is carrying the load with the AC and lights on without issues. I will attempt to recharge the Hawkers since they are only 3 years old.
 
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