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Delco 10si Alternator

D

Denny K

Member
Mine is putting out about 17.5 volts instead of the usual 13.5-14. Voltage Regulator? Diode Trio? Rectifier? I know there are some very knowledgeable people here that will know. Its a 2 wire conversion on a 8-N Ford. Done lots of years ago and worked well until now.
 
could be regulator, cost to repair alternator is probably more than an entire rebuilt one at auto parts store.
 
If the #2 terminal is not connected to the output stud, it could do that. If it is connected, it needs a regulator. Jim
 
Yes , #2 is connected. It wasn't charging so I took it apart and put new brushes in it. Old ones were still fair. Voltage Reg. spade terminals were very rusty so I wire brushed clean and reinstalled. Now it charges too much.
I see on the IH parts they have a VR for 1086 ect, ect. for $5.93 so I may get one.
 
Very easy to take apart and install new regulator if he already installed new brushes him self. Just be careful to put insulated screws in proper holes. How?re when installing brushes as I recall regulaterhar to be removed or at least screws removed. If you mixed plastic shielded screws in wrong holes alanator will full field producing high voltage. Screw holding metal part or regulates with tab aligning with D hoke in back must have plastic insulation.
 
(quoted from post at 17:41:12 04/16/19) Very easy to take apart and install new regulator if he already installed new brushes him self. Just be careful to put insulated screws in proper holes. How?re when installing brushes as I recall regulaterhar to be removed or at least screws removed. If you mixed plastic shielded screws in wrong holes alanator will full field producing high voltage. Screw holding metal part or regulates with tab aligning with D hoke in back must have plastic insulation.
Click to expand...
wo of the 3 screws need insulators. Only the one closest to edge of alt housing end of resistor is without insulator. The likely one missing an insulator is the one Wilson mentioned, near the "D"-hole.
 
Thanks to all the good comments. I will check out the insulated screws when I get a chance. Did not realize or notice the insulated screws had a specific location. May take a few days until I can check it out.
 
Also make sure the number two terminal is in good shape, clean and tight on regulator spade.. A poor connection on number two will cause over charge because it cannot sense voltage output properly.
 
Hello denny k,

The regulator needs ground to work also. Make sure the alternator is making a good ground,

Guido.
 
(quoted from post at 19:54:29 04/16/19) Also make sure the number two terminal is in good shape, clean and tight on regulator spade.. A poor connection on number two will cause over charge because it cannot sense voltage output properly.
Click to expand...
little knowledge is dangerous. It depends on the age of the VR in the 10SI. Older units will go full bore if sense is lost & later units will shut down entirely if sense is lost.
 
When I was repairing those alternators, just to prove a point to fellow workers and customers, I would hook a variable resistor into the sense lead while I had it on the test stand. With full battery voltage, zero resistance wire hooked to sense terminal on regulator, the alternator would operate at normal voltage. The voltage depended on what regulator was in alternator as some manufacturers lowered the regulated voltage down just below 14 volts to help extend battery life on tractors. Most regulated right about 14.5 volts though.

Then I would increase the resistance in the sense lead and the voltage would keep on rising up to 19 volts or more. This test was to simulate a poor connection. Opening the circuit completely would shut charging off completely.

I also applied a load on my test battery to check for full rated amperage output of alternator at above normal full charge battery voltage of 12.6 volts. I don't recall ever testing an alternator that charged with the sense lead open, disconnected.

Those tests would date from about 1975 until around 2012.
 
(quoted from post at 18:34:14 04/17/19) When I was repairing those alternators, just to prove a point to fellow workers and customers, I would hook a variable resistor into the sense lead while I had it on the test stand. With full battery voltage, zero resistance wire hooked to sense terminal on regulator, the alternator would operate at normal voltage. The voltage depended on what regulator was in alternator as some manufacturers lowered the regulated voltage down just below 14 volts to help extend battery life on tractors. Most regulated right about 14.5 volts though.

Then I would increase the resistance in the sense lead and the voltage would keep on rising up to 19 volts or more. This test was to simulate a poor connection. Opening the circuit completely would shut charging off completely.

I also applied a load on my test battery to check for full rated amperage output of alternator at above normal full charge battery voltage of 12.6 volts. I don't recall ever testing an alternator that charged with the sense lead open, disconnected.

Those tests would date from about 1975 until around 2012.
Click to expand...
have both the older & newer and they do as I said. You can examine the regulator circuits (old & newer) and see the added transistor which functions to shut down output when sense is lost. That 'extra' transistor is not in the old units that go full bore when sense is lost.
 
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