Another alternator bites the dust

What is it with alternators…. 18 month old modern Delco style altenrator failed on Friday on the way from Miami to Georgia. Ended up waiting 90 minutes for Hagerty to send a flat bed followed by another 80 minutes truck ride to our destination.

Incidentally, just two days before marked the 25th ownership anniversary (and yes I found it here on JL) and the first time in well over 100k miles that I have to finish a run on a flatbed! *

Since I always carry a spare, I was able to change it in my dad’s garage in a little over 2 hours. Car ran great today on the way to eastern TN

I just have bad luck with alternators… first long trip with the car in Oct 99 to the JCNA festival in Colorado Springs, I ended up replacing the original Butec somewhere in Kansas around midnight… this one was only a year and a half old… another sign that the quality of parts is going down the tubes.


  • Technically it s the second time I had to get a tow in 25 years although the first time was operator error. Top of pikes peak in 99, car wouldn’t start. Night drive on a flatbed down pikes peak was spectacular and made up for the embarrassment of realizing the car didn’t start because I forgot the kill switch!

Sorry to hear this. Just curious, was it new or rebuilt, and do you know what the failure was?

see amazon es 1002c…in essence a cs-130…of course, if it is good it will be sold out…and it is

I’ve been lucky I guess. Lucas alternators, many failures, last one had a short and partially melted internally. It had been rebuilt by a reputable builder 15 years before and had maybe 100 miles on it. Since late 70’s I’ve used Delcos - 4 I think in total in maybe 5 cars - the first was off a 60’s Firebird. I wired it in with a mechanical regulator from Chrysler, ran it maybe 15 years. Don’t know what happened to it, probably sold on a car.

The Delco 10si or 12si (your pict) are both very dependable long lived alternators with a big range of output options. But everyone makes them these days and they are not all the same.
Powermaster make a good product and a range in those models up to a Polished Alum one that matches the early style cam covers.
The 10si on my 62 S1 was rebuilt by a local mom and pop shop and has been on the car for 15 years.

There are (at least) two modern alternator problems

A very large % of non-OE alts are made in China. Typical early failure is diodes

“rebuilt” units available in USA are reported as often being very poor quality

I recently had a rash of OE Denso alternator failures

out of 7 original units, 5 experienced, or already had, failed diodes

No replacement rectifiers are available. They all failed after 25 years

The Chinese Denso replacements have an expected diode lifespan of ~3 years according to my auto electrician mate, who is vastly experienced

It is possible to get quite expensive Chinese made Denso replacements
Its likely they have better quality diodes and other parts

What is the nature of your failure ?

Not sure what the failure was, will get it rebuilt when I get back, or maybe try to find a better quality one. Must be the diodes or regulator.

This trend of low quality Chinese manufacturing is a real PITA and affecting every sector and reputable brand. Couple of years ago we had a pair of 2000hp MTU marine diesel rebuilt using only MTU parts. Well the new starter was made in china and lasted 4 months. Thank I had the old one rebuilt… the crankshaft, pretty big on a 16v2000, was made in India then shipped to MTU in Germany for inspection before being shipped to the US.

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Overall I have had good luck with the Delco’s in my 70s Chevrolets but a few years ago I bought a rebuilt one from O’Reilly since the one in my '74 was very old and sometimes slow to come on line after start up. The rebuilt one did not last 30 miles before it started squealing. Lucky that it did not grenade on the freeway. I made it a couple of miles to home but the cap on the back was gone and the shaft was flopping around. O’Reilly gave me a replacement but I put the old reliable one back in instead.

68 E-type FHC

I just keep recycling my 11AC Lucas units. I have a 52 year old one in one car, a Chinese two wire in our XJ6 and I’ve just put another regulator in the spare 11AC.
The aftermarket regs are set in epoxy (as were the originals) and are of questionable durability - your’s for less than $10 on eBay. I’ve pulled one down with the intention of making one up myself that I will fix externally. Perhaps the old Lucas mechanicals and a bespoke home made reg might do the trick?
PS. I always take the spare on trips - expecting the Chinese two wire to crap out at the point of maximum inconvenience.

I have fitted Hella/Bosch units over the last 10 years. They are 55a, self regulating units and I have never had a failure.

These were fitted to gazillions of mainstream cars (mainly Ford) mainly in the 80’s/90’s and the fit the E type with no mods apart for the wiring.

It means you can remove the control unit from the circuit.

I used to pay £65, now they are at least double that I think.

Hi Pascal. Chinese quality control is iffy at best. With Chinese made alternators, there is a grading system: 1 thru 5. 5 being the best. I was never able to determine how to assure to get a Grade 5 however other than the best may cost more. My solution was to buy a made-in-USA Delco. Not a Delco made elsewhere. A CS-130 (non AC model with 85 amps was my choice) is, IMO, preferable to either the 10si or the 12si because DELCO went to quite an effort to quiet their alternators both electrically and mechanically and that result was the CS-130. I found a NOS government surplus Delco alternator on eBay for $80. They are out there and worth the effort to find.

I had a 78 Ford Fiesta, put three regulators in it.

One thing that may make it difficult to change is that the alternator is mounted backwards, I need to be sure I get one that will work in reverse

The only difference is the fan. Swap fans and your good.

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Try the Mercruiser swap.


Just adding that I tried the Mercruiser swap on my S2 and could not for the life of me figure out a way to fit/mount it without serious modifications - either forward or backwards. Could just be me having serious “mechanics block” that day.

Where did you have problems? I found that it was a drop-in, other than the tensioning arm needing some light machining.

There is no way the alternator pulley lines up when mounted in the stock location. And it’s not a matter of adding washers, as the alignment is off by inches. I didn’t even get to modifying the tension arm.

What year is your car? I have a '69 with the older style reverse mount, and the pulley is not a problem, only two washers were needed to position it perfectly. Or is this a different alternator?

69’ with the standard (non reverse) mount. Possible I got the wrong part, but used the Mercruiser part number referenced above.