Alternator draining battery

johnnymac · Jul 25, 2009

Does anyone know why an alternator would drain the battery? I was having problems with my alternator not regulating the voltage so I took it to get repaired. The repair shopd replaced the voltage regulator and the recitifier. Unfortunately, the repair shop thought that it was a 100amp alt and I've been through 2 rectifiers before he relized that he wasn't puting in the correct rectifier. When he finally put in a 140 amp rectifier, it finally worked properly, but now it is draining the battery. What would cause this? I haven't worked on an alternator before and the repair shop is getting rather annoyed with me returning to them. (and I'm getting annoyed having to deal with this damn alternator).

I always thought that this was a 12si .... but the shop swears that it is a 10si, could that be the source of the problem?

markw · Jul 25, 2009

http://www.madelectrical.com/electricaltech/delcoremy.shtml Based on the cooling holes in the back it looks like a 10si with a 1 wire conversion. What problems made you take it in for repair the first time? Are you sure you don't have something else draining the battery?

john68 · Jul 25, 2009

Nice to see those pictures again, you were here about 2 weeks ago,

johnnymac · Jul 25, 2009

The original problem was that the voltage was spiking to 16+ volts when I reved the engine.. So I took it to a alternator/generator repair shop.

I just ordered the Summit 140 amp alternator to replace this one.

1969SSBB · Jul 26, 2009

Sounds like an internal ground on the alternator to me. Do you have a clip-on ammeter so you can check for any current flow on the lead going to the alternator?

Dan 69 LeMans Blue 454 AC PDB PS

stellar · Jul 27, 2009

It is a 10SI . There are different ways to make a 1 wire alt. Some will have a small drain and some won't. even at that it is minimal and would take a long time to drain a bat. So most likley there is still a problem in the alt either reg or rectifier. If there is a competing shop in the area take it there and I bet they will tell you what is going on.

johnnymac · Aug 4, 2009

I swear... I need to get an exorcist for my car! I took it to a performance car shop today to get their opinon on my suspension issues that I have been having. As I pulled up to the shop, my MagnaFuel pump completely froze up and shut down. We tested the wiring thinking that perhaps an inline fuse blew.... but we couldn't find anything because the wire disappeared behind the kick panel (which I didn't want to pay for the tech to take off the parking brake assembly to test and investigate -and I cou;dn't exactly do it myself since I was stuck there).... so we ran a completely new wire to the pump and tested it with a light.... and it worked. Then we plugged in the pump and it blew the fuse.

I swear, it's one thing after another. I think that the reason the pump went bad was because of all of the voltage spikes I was having due to the alternator spiking the system.

I have sent it off to MagnaFuel to have it rebuilt as it is a lot cheaper than buying a new one.

If anyone knows of a good car exorcist here in St. Louis, PLEASE let me know. :-(

Also, the above listed alternator is the Summit Brand 140 amp alternator. It is advertised as a 12si..... but clearly isn't. http://www.summitracing.com/parts/SUM-810351/ I bought it thinking that I would go from the 10si to the 12si.... but I got the exact same alternator that I was trying to replace!

Steiner · Aug 4, 2009

DB has a chrome 12SI for a pretty good price at $90, but it's a 110A model (70A at idle). I've got their chrome 10SI one and am happy with it. You can call them and they'll set you up with one wire, three wire, v or serpentine pulley.

http://stores.channeladvisor.com/db...chrome alt 1-wire&caTitle=NEW CHROME CHEVY ALTERNATOR 110 Amp 12SI 1-Wire 65-85

AJSZR2326 · Aug 4, 2009

dont give up ! is the alt getting hot w/ engine off and key on? what voltage is at the alt when running? 1 -wire's have have internal rect that starts at 2500-3000 rpm to activate. are you running 1 wire to battery only?do you still have external v/r ? do you have a voltmeter?

johnnymac · Aug 4, 2009

Yes, my old one would get hot when the engine wasn't running and without the key even being on. I have since put in an older one that works, but I am not going to install the one that I received from Summit since it is the exact same one that went bad very quickly. I wil be returning it this week and then getting one from DB's as posted above. According to the Alternator repair shop that attempted to repair my old Summit one, "The parts are all made in China and will not last because they were never designed to run at such high amperage."

I think that my best bet is to get one from DB's which says it is a Delco 10si (as oppossed to the Summit which is incrrectly labeled as a 12si but is a 10si.) AND DB's has a no questions asked 1 year warranty.

Steiner · Aug 5, 2009

johnnymac said:
I think that my best bet is to get one from DB's which says it is a Delco 10si (as oppossed to the Summit which is incrrectly labeled as a 12si but is a 10si.) AND DB's has a no questions asked 1 year warranty.

Just so you know, DB has both 10SI and 12SI. If you put "12SI" in the search box on their home page it will come up. I could see why the 10SI might be a better choice as it's $20 less and only down 5A. Plus, it clearly says it's a Delco unit whereas the 12SI is called an "aftermarket" unit. You have to call them to get the serpentine pulley though and it's the same price.

I've got the 10SI 105A one and also have purchased two of their PMGR mini starters and am very happy with everything.

Alternator draining battery

johnnymac

markw

john68

johnnymac

1969SSBB

stellar

johnnymac

Steiner

AJSZR2326

johnnymac

Steiner

Top Contributors this Month

Recommended Communities