Technical Now What Did I Break?

I went to check the timing on my car. 350sbc. I hooked up the timing light, using the positive post on the back of the one wire alternator. I started the car and picked up the timing light, the clip on the positive post rotated back and made contact with the alt case. Luckily, I was right there but still managed to melt about 8 inches of wire.
I looked over the entire wire and saw no further damage. I cut out the section of bad wire and spliced in new. But upon starting the car I noticed it's not charging now. Anything to check? Or just buy a new alternator?

 

Check to make sure you have 12v at the alt terminal with the car off (possibly key on depending on what harness is in the car). If you have 12v and still not charging you might have killed the alt. Also put on some clips with a cover that goes to the end on the timing light or use the starter solenoid if you have an external one.

 

If all wiring is ok you might have blown the diode on the alternator, Chevy alternators are easy to rebuild if you can find a kit, kits used to have bearing diodes and brushes
Dan

 

eBay has several

https://www.ebay.com/itm/384364324341?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&mkscid=101&itemid=384364324341&targetid=1645685073328&device=m&mktype=pla&googleloc=9019269&poi=&campaignid=20133407470&mkgroupid=147476396765&rlsatarget=pla-1645685073328&abcId=9312979&merchantid=511552112&gad_source=1&gbraid=0AAAAAD_QDh94yj9FSr91uC-U8IOEkuTHu&gclid=CjwKCAjw34qzBhBmEiwAOUQcFy0i7cvSMzDrh8G8ImJ5ftqOqP0FZy_w86GiLe2wgX18HussWbZ2pxoCLvAQAvD_BwE

 

I remember picking up a rebuild kit, and nut driver set, to repair GM alternator on way home from rod show, at a Meier's store. Oops, that was 30 years ago!

 

You have let the magic smoke out of the diodes. Time for a replacement diode or alternator.

 

I run my timing light off a spare battery since no good + post is available under the hood. Suggestion does do much good know though...

 

is the wiring harness from a car in the seventies or eighties? they used a fusible link wire or plastic fusible link in the wires near the starter

 

I made the harness with no fuse in the line. It goes from the alt to the starter solenoid. I still read 11+ volts at the alternator so I believe the wire is in good shape.

 

Unless that 11+ volts is all the battery has, 11 volts on a 12 volt system is a problem. There is a bad connection someplace. A fully charged 12 volt battery should have at least 12.4 volts.

 

Yeah, with car off the battery reads 11 volts due to the fact that it is not being charged the last couple of trips around town. The battery is only a few months old. When the car is running it still only reads 11 volts. After reading some of the replies, I think a rebuild kit is in order. Thanks, everyone.

 

I opened it up. I don't see anything melted. I guess I would need to change that thing that I am guessing is a capacitor? I don't see that part in the posted rebuild kit. Is that a common part to go bad? This would be a first rebuild for me. It looks pretty straight forward but any advice is appreciated.

 

The capacitor seldom goes bad. I've never seen one bad , and it shouldn't cause a no charge situation anyway. Looks like yours has no diode trio, so most likely problems (if the alternator is the problem) will be rectifier or regulator. The one wire unit uses a different regulator I believe so be sure to get that correct. I do find it hard to believe the short killed the alt...all the current flow was from the clip to the other end of the wire, wherever that is hooked up to power. I'd make darn sure that circuit is good, even to the point of running a jumper wire from battery + to the alternator out put terminal..just for testing.

 

When ordering a rebuild kit make sure you get the corresponding kit for your alternator. Yours looks a little different ,I think, than the ones I rebuilt, been a while.
Dan

 

Actually you could reassemble and take to local auto parts store, they can test your alternator for free

Dan

 

If that battery only has 11 volts, you need to put it on a real battery charger. Its possible the thing that got damaged was the battery itself. You need to remove the battery post connections and hook the battery charger directly to the battery for at least an hour and a half. Any voltage below 12. 4 volts is considered a low charge, 11 volts is in the junk battery range, and it may not take a charge at all. Put a battery charger on the battery and see if the battery voltage comes back up to 12.4 volts.

The alt probably doesn't have the capacity to charge a battery with less then 12 volts in it.

 

Thanks, I put the alternator back on the car and drove to Autozone. They tested battery and alternator. They said the alternator is bad. So, it looks like a cheap fix with the rebuild kit.

 

All the rebuild kits have this part but, I don't see it inside my alternator.

.

 

Joe that is the diode is your alternator a one wire alternator?
Dan

 

yes.

 

The diode I believe is under the aluminum heat sink (on the right side of your picture) been a while since I’ve rebuilt an alternator like 20 years.
Dan

 

Ok, I'll probably see it once I tear into it. thanks.

 

Joe I think you might need a rectifier (heat sink looking object) this link might help you, not sure what alternator you have.
https://store.alternatorparts.com/15si-rectifier.aspx
A good YouTube video also


Dan

 

Been a while since I've been into one, but I believe the diode is bolted to the top of the rectifier(finned piece), 3 nuts in a row, and the leg of it bolts to the regulator. Notice you have a pin in the brush holder, don't forget to take it out once it's back together(past experience)
Not sure how the one wire setup uses the diode from the kits, you'll need some more research.

 

I was thinking that on a one wire the difference was the self exciting system in the regulator it's self.
This kit shows the diode trio but you still have to test the rectifier/diode bridge or what ever name is tagged on it your hood.

The second kit is a complete with all the goodies but at 32.14 plus 7 bucks shipping 39.14 you have a fully rebuilt one wire alternator.

 

2x on the second kit
Dan

 

I was curious as to the 2 red jumper wires in your alternator. A little internet search, found one vendor with 10 different regulator listed for the 10SI alternator! Two of them showed red jumpers in the image, one of those stated that the diode trio is eliminated with that specific one. So, bottom line follow the instructions with whatever you buy!
Happy charging.

fyi https://store.alternatorparts.com/10si-regulator.aspx

 

I was confused by that myself. I was wondering if I buy the kit. Do I keep the jumper wires I have and leave out the diode trio? I am thinking to make it all match correctly is to replace everything I have with the new kit. However, what the heck is the thing in the red circle? I don't have one and it doesn't look like it comes with any of the kits.

 

Looks like a resistor or a fuse not sure, but my thinking says if the new voltage regulator doesn’t have one you should be ok your alt looks different than what I remember, does your new kit have instructions? Or an explanation on parts or tech phone #?
Dan

 

I didn't buy a kit yet.
It's always something.... The job itself it so friggin easy only to be bogged down by lack of knowledge of the components We'll all get it figured out