olds 307 and 403

Ok I had the usual 10si chrome high output alternators that either way overcharged or died after a couple of years. I then went to a CS130 100 amp replacement for my 1988 Cutlass Supreme Classic wired through the factory oil/choke light, why GM labeled these Olds V/8 hot air choke cars this way is beyond me. My 81 Delta 88 was the same way. I also have it hooked up to a Sunpro voltage gauge, reads 1 volt lower than what two multimeters told me. It charged fine for a year and then died. AC Delco Mexican reman. Where I bought it could find a replacement anywhere. So they went through another supplier. I ended up with 12si 94 amp replacement. I was happy with it being a high output 12si replacement. Ever since I have put it on, it needs revved up to charge. This is shown by light on in the dash and the Sunpro volt meter. Pretty sure I checked it with the multimeter as well. Is this the norm for replacement voltage regulators? Once excited, it charges with no issues. Is there a reasonal priced replacement that is only 3 wire? It should charge right away since I am running it through the idiot light circuit, would be nice to have instant charging. Thoughts?

joe_padavano

"One wire" alternators were never factory installed. ALL replacement SI alternators are three wire (and by "replacement" I mean direct replacement, not the universal ones sold by Summit, Jegs, etc).

I remain mystified by the problems people seem to have with these. In 45 years of driving, I've never had this issue when I rebuilt the alternator myself. I DID recently install an AutoZone rebuilt in my wife's 85 D88. It lasted about two weeks. I've since rebuilt the original and it works fine.

Message: rebuilt alternators are crap. Buy the parts and do your own.

stellar

No reason to be mystified Joe. Take the Auto Zone one apart and You may see some half a$$ed parts or work. I have been rebuilding professionally since 1975 and I have seen some real shoddy work and cheapo parts being used in the big box stores rebuilt alternators and starters. I have rebuilt thousands of alternators and seldom have a problem. If you use quality parts and have pride in your work things work just fine. The original post sounds like it has a 1 wire regulator in it. Take it apart and put in a 3 wire reg and all should be well.

joe_padavano

Read it again. He says he got a 94A 12SI replacement alterantor. That's a three wire unit as used on late 1980s Caddys with the 307.

Olds64

To the OP, don't be confused by your alternator not charging at idle. I just replaced a 10si 100A Jegs alternator that died with a 10si 108A alternator. Here's some good reading:

http://www.madelectrical.com/electri...elcoremy.shtml

Here's the alternator I just installed:

https://www.oreillyauto.com/detail/u...10040=Show+All

joe_padavano

I've never had a problem with an SI alternator charging at idle. I only use replacement style three wire versions. There was never a 108A factory SI, so apparently even that Oreilly unit is not a factory replacement unit. I'd never buy one from Summit/Jegs/etc.

Olds64

Well, the Jegs alternator I had lasted about 5 years. That's pretty decent in my book.

As far as the 108A alternator goes, at first I thought it was for a 76 Olds 98, but then I recall that I found it listed under an 86 Chevy K20 pickup with the 6.2L Detroit diesel. I did quite a bit of research before purchasing a replacement alternator and so far it's working great. Plus, now I have a lifetime warranty.

joe_padavano

There was never a factory SI alternator with more than 94A. Anything over that is an aftermarket design.

Olds64

Well, then I guess it's either an "aftermarket design" or O'reilly and Rock Auto mislabeled the current rating of a stock alternator. Either way it works great.

stellar

17SI came in 108 amp factory delco.

stellar

1988 Cutlass supreme came stock with a 78 amp 12 SI alt. The 12 SI 94 amp is a good upgrade and should start charging without needing to rev the engine. It is not the norm for replacement regulators if using a 3 wire reg. It is common if it was rebuilt using a 1 wire reg with a light function. If it was rebuilt with a 3 wire reg and it needs to be reved to charge, I can think of 3 possible problems with the alt. 1. defective reg. 2. A mismatch of the rotor and stator (using a rotor from a 10DN or 10SI alt with the 94 amp 12 SI stator). 3. Too large of an air gap between the rotor and stator. usually due to low quality aftermarket stator or a rewound stator that had a bit too much material cleaned up from the inside of the stator. Maybe you can exchange it for another 94 amp where you bought it.

stellar

The 86 K20 6.2 D came stock with a 78 amp 12SI or a 108 amp 17SI. So not mislabled.

Olds64

I guess the alternator I have is a 17SI then.

I stand corrected, I could have sworn I read on madelectrical.com that the 10SI and 12SI alternators didn't charge well at idle. I do recall reading this:

The 17SI alternator I installed on my 71 98 was "slightly" larger than the Jegs 10SI alternator that I had previously. I had to modify the stock brackets by drilling out a few of the holes larger.

olds 307 and 403

I have rebuilt a few alternators, including pressing bearings out and in. Unfortunately someone stuck a 10si in it, was 78 amp and wanted more. The 10si just don't last at 100+ amps, not enough cooling. Is there a good replacement 3 wire voltage regulator that lasts?

stellar

For an alternator or regulator to last conditions must be optimal. That would mean good connections, wiring, a good battery, as well as an alternator capable and suitable for the load demand. For the regulator to last the internal windings should be matched. This will assure the best performance, output curve, and reliability. First you need to know what stator is being used (amperage) and then a rotor to match the stator and then you can determine what regulator to use. If the alt has been rebuilt with mismatched parts, your best hope for a reg that will last is to determine what rotor is in there and get a reg to match the rotor. Most Delco rotors had a number stamped on them. If it is an aftermarket rotor you will need to make an amp draw or resistance test to determine what rotor it is.

oldcutlass

Alternators should last a whole lot more than 5 years.

Olds64

Well, given how little I drove my Olds during that time you're probably right. I guess it shows it was cheap Chinese junk. I was happy with it, but I didn't want to replace it with another one that didn't have a warranty. So, I found one that's even better and has a lifetime warranty. Now my generator light works again; plus, I don't have to worry about that unsightly voltage regulator on the firewall.

olds 307 and 403

I am using a 4 gauge cable to the alternator and 1 gauge battery cables with everything tight. The alternators go for many years, 5 is about max on the high amp 10si. Not sure why the aftermarket didn't copy the 12si, would actually last.