10SI Delco alternator problem

[Gene Davis (Ga.)]

On my standby generator I have a 1SI Delco alternator that is wired with the battery wire to the rear post and the 2 small wires of the plug on the side connected to the ignition switch. It has worked well for about 10 years and suddenly last time I used it the alternator would not charge. Did the old trick of inserting a drill bit in the case to ground the regulator test tab and it charged like the proverbial scalded ape and when I removed the drill bit it did not charge. Supposedly that meant the regulator is bad, finally after much looking found a regulator in a parts store, most of them want to sell a whole rebuilt alternator instead of a part to repair it. Installed the regulator in about 45 minutes time and cranked it back up. Same thing again, charge with tab grounded and no charge if not grounded. Had another good alternator, took the regulator out and changed it in to this one and same story, Did this with a third regulator and the same old story. Any body know whart might be going on here??

 

[Gene Davis (Ga.)]

Meant to say it is a 10 SI alternator. Please overlook the typo error.

 

[RodinNS]

Dunno...... That's why I put em on the counter and tell them to 'Give me another one", and then go and install the new alt.
Buying the ONE reg was probably a good percentage of what the rebuild is worth.

It would seem that the reg itself is not properly grounded mabey? Does the alternator itself have a ground wire or rely on the mounts?
Again, I'm only stabbing in the dark since I don't bother with rebuilding them.

Rod

 

[Anonymous-0]

Two things come to mind, the old regulator failed, and when you installed the new one you got a mounting screw in the wrong position.
The one without the plastic insulating sleeve must be closest to the outer edge of the case. The ones with the insulating sleeves must be in the inboard holes.
If you got the uninsulated screw where the diode trio connects, it may have blown the trio.
An insulated screw with a damaged or missing insulator would have the same effect.

Normally the regulator should be wired so the #2 wire sees constant battery voltage, usually from the BAT stud on the alternator rear.
The regulator #1 wire needs to have switched power as in your ignition switch.
I have seen aftermarket regulators in the last 10 years that will not allow the regulator to Excite unless the #2 wire has battery voltage, check that wire for voltage.

 

[Bob]

Gene, did you check all 6 diodes in the rectifier, as well as the three in the diode trio (or replace it with a new one)?

When you get it going again, connect the #2 terminal over to the large output stud, and the #1 terminal to the ignition switch, using a diode, a resistor or an "idiot light" in that lead, to prevent a re-occurrance of the problem you are now having, in the future.

(Without a resistor, a diode, or an "idiot lamp" in the "excite circuit, excessive current can backfeed out of the alternator through the #1 terminal, under certain conditions, destroying the regulator and/or the diode trio.)

<img src = "http://ndtc3500.stellarnet.com/~blweltin/Bob/AlternatorHarness3.jpg">

 

[Goose]

Could be the diodes went kaput, although it's rare for all three to fail at once.

 

[Anonymous-0]

Another thing that will instantly kill a regulator is to reasemble the alternator and forget to remove the little wire your using to hold the brushes retracted. This little wire puts a dead short across the regulator and destroys it the instant you apply power to the #1 regulator wire. Don't ask me how I know this (BLUSH) ;-)

 

[Anonymous-0]

I have had a a 10si "one wire" alternator on a Super A for about 4 years and about 2 month ago it stopped charging. I found out that the alternator was not getting a good ground through the mounting bracket/bolts. Ran a separate ground wire from the alternator to the engine block and that fixed the problem. You might want to try that on yours.
Pete

 

[Anonymous-0]

Like said could be bad diodes easy to check with multi meter. Old Motors manuals have good instructions on 10SI rebuilding and trouble shooting.

http://www.alternatorparts.com/FAQ.htm
Mad Tech Info

 

[onefarmer]

If it charges using the drill bit test, check to see if the two terminals are getting power, expecially the number one terminal. If it is putting out 30-40 amps with the drill bit test the rectifier is probably ok. Maybe the diode trio is caput. You should, as others said, checked it out when it was apart for the reg replace. Easy test with an ohm meter. Continuity with the leads one way for each diode and none with the leads reversed.

 

[Larry59]

This picture sure helped me understand a problem I to am having with this tractor I just got yesterday. Thanks *S