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Super C Alternator

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WayneMo

Member
My Super C has a GM 10 SI Alternator that works fine when running but it has a drain on the battery when it is not running that will drain the battery over time. Is the drain due to faulty diodes in either the voltage regulator, Triode, or Rectifier? I see there are kits sold with various combinations of these 3 parts. If I knew which was faulty, I could order the right parts and fix it myself perhaps.
Or should I just get a rebuilt alternator at the parts store? Kits run about $15 to $20 depending on parts included in them. I don't know what a rebuilt one would cost.
If I knew which component was at fault, I could just buy it alone very cheap also.
Your advice?
 
you have to find out first if that is what is causeing your problem. put test lamp between ground cable and grd. post on bat. and start disconnecting until lite goes out.
 
1 wire or 3 wire alternator?? If 1 wire common problem if 3 wire is the #1 wire going to a switched wire or is it hot all the time?
 
This is a complaint with some ?one wire? or ?self exciting? Delco 10SI alternators. Culprit is likely the regulator, although a leaky diode is a possibility

I have rebuilt several Delco 10 SI alternators with a 3 wire repair kit. For about $22 I can get a kit with bearings, brushes, rectifier diode, diode trio, and regulator. A wire from #1 pin on regulator to switched ignition source is all that is needed to excite the 3 wire alternator. Add a diode or lamp in the line to prevent engine run on when switch is turned off. #2 pin on regulator can loop down to output stud.

Other than a press for the bearings the parts are not difficult to change. All screw connections on 10 SI, no soldering necessary. You can get a rebuilt starting at around $35, but I like the satisfaction of doing it myself.

If this only happens when it sits for an extended time another option is to disconnect battery negative cable or install a cut off switch between battery negative post and frame.
 
Hi....Yes, I essentially did that, but used a meter instead of a test light and the meter shows 12v between the loose cable and the battery terminal which to me means there is current flow when the cable is connected to the battery.
The voltage dropped to 0 volts when I pulled the alternator output wire off and remained 12v with the plastic connector removed alone.
 
Hi...Yes the battery will hold a charge disconnected. I had not started this tractor for several months but recalled the battery did drain back then. I also had a problem with the starter motor switch shorting out and replaced it and even had to add some insulation to the new switch to prevent it shorting out. I guess the switch was made in China or had some defect in it.
I am pretty sure the alternator has a problem since the loose battery cable shows 12v between it and the battery terminal.
 
Hi...My alternator has a plastic connector with 2 wires inside it and then a large output wire terminal feeding voltage to the battery. Is that a 3 wire system or 1 wire because of the output.
 
Hi...I guess mine is a 3 wire system since it has a plastic connector with 2 wires in it and then a single output terminal.
There is another wire looped down to the output terminal. Is that all you need to excite the alternator or do you need a diode in that wire? I do not know if mine has a tiny diode in that wire but the system has worked great for several years.
Sounds like I could just replace the bad part for less than $10 if I only knew which part was defective. Otherwise I am tempted to get the kit for $20 and try to fix it myself. I am learning a lot from folks on these boards.
 
If the plug has 2 wires coming out of it then it is a 3 wire. #1 wire should go to the ignition side of the switch or as I do the ignition side of the coil. The #2 wire should go to the big charge stud and the wire off the charge stud should go o the amp gauge
 
Thanks, mine is a 3 wire system and it is wired as you described. I think there might be a diode hidden somewhere to prevent motor from running on. I am looking for a diagram that shows all this.........Folks on these boards are a real asset!
 
I do not have a diagram but I can talk a person threw it. My e-mail is open if you think talking on the phone would help you
 
Sounds like your problem is in the rectifier assy, a leaking diode, OR the rectifier may be coated with conductive brush dust.
Remove the rectifier assy and spray it down good with electrical cleaner then dry with high pressure compressed air.

After cleaning, test all 6 diodes for leakage or open with an ohmmeter. It may be defective, but also may just be dirty with conductive brush dust. Clean and check it before discarding it as defective.
 
I forgot to add, check or just remove the electrical noise condenser that connects to the rectifier assy in the rear half of the alternator case. It might have some electrical leakage causing your battery drain.
 
Hi...I am learning a lot from the guru's on this site, thanks to all!
I have a rebuild kit ordered and will try to fix it myself. I will look at the "'dust" accumulation. I guess you have to unsolder the diode leads to check them though. The condenser is not needed I believe, it is only for radio noise.
 
Nothing to unsolder, just check between the pos or neg half of the heat sink and the copper strips at the stator connecting bolts.
 
No, the diode or idiot light is to prevent or restrict backfeed from the alternator to the ignition to prevent running with the ignition switch off.
 
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