Internally reglulated alternator

[Morgan3820]

Is there a way to tell if an alternator is, or is not, internally regulated? I picked up a non yanmar alternator. The only connectors on the back are the 'L' sensors and the (+). No earth stud so I assume that it is grounded through the chassis.

[r.furborough]

I think you have an internally regulated alternator as there is no connection to the field windings for an external regulator.

The following may help

Common Alternator Wiring Terminal Letter Designations

B+ , 30, Battery Positive
S, M, 2, Battery Voltage Sense
B- , 31, D-,GRD Battery Negative
F, DF , 67 , FLD , EXC, Field/Rotor
D+, 61 , L , IND, Charge Warning Lamp
DFM , FR, SIG, C, M, Digital Field Monitor output for computer ECU control
IG, 15 , R , Ignition
N, C, Central Point
W, P, STA, Tachograph rev counter (stator single phase tap AC output)
D Dummy

[cardiacpaul]

grab a number off of it if there is one, or post a photo... that'd help

[hellosailor]

Get the model number and look it up. Somewhere on that alternator are numbers, and they'll tell you what you have. If it was rebuilt by itinerant jokers who ground off all the numbers...you can still open it up and look inside to see if there's a regulator. Or, ask someplace that sells and services alterantors what you've got.

And old used anonymous alternator wouldn't seem too reliable to start with, even compared to buying a cheap one from a junkyard.

[tytower]

The L stands for lamp. The above poster has put this in for you.Positive is fed from the battery through a lamp on the dash down to the L terminal which in fact is a Diode. When the alternator starts to turn the current flowing through this Diode circuit excites the field and the built in regulator takes over.

The + terminal is simply conected into the Battery Positive wire somewhere. This feeds the charge to the battery.

Best type of Alternator to have in my opinion.