OE alternators

[Donald]

No, a diode as part of a rectifier network can fail in a way that it starts letting current through imperfectly causing a high ripple. That's why those handheld testers report on ripple. If you have >100mV your car will still likely function but it's an indication you have a diode starting to go. It's a very tricky thing to diagnose and may cause weird gremlins to happen in the car's electrical.

There absolutely are bad rebuild shops. Unless you are hovering over the guy's shoulder you have absolutely no assurance that all the necessary parts were replaced, and of good quality. A unit can be built with crappy parts and still test well electrically or function for a long time. There's dozens of ways that shortcuts can be taken. Using generic voltage voltage regulators is a prime example. If the guy is only charging $100 for a rebuild do you really think he's sourcing an OE regulator which costs at minimum $50?

I still think you are not correct. A single diode cannot fail in the way you describe. A full wave bridge of 6 diodes can have a single diode fail and produce ripple. But a single working diode will never be what causes ripple because it's a cheap version.

 

[nobb]

I still think you are not correct. A single diode cannot fail in the way you describe. A full wave bridge of 6 diodes can have a single diode fail and produce ripple. But a single working diode will never be what causes ripple because it's a cheap version.

Diode(s) can indeed have an intermittent failure at higher temperatures, they develop microscopic cracks. Whether a cheap vs brand name diode is equivalent in quality is not the primary problem. A shop is most likely reusing the same diode pack in a rebuild if it tests fine. But a bench test at room temperature is different than while operating in a hot engine bay. In 99% cases it's not a problem, but you could very well get an intermittent/gradual failure over time that goes unnoticed until it eventually leads to a misfire that you spend a bunch of time chasing with no idea why.

 

[zzyzzx]

Auto parts suppliers don't make their own diodes!

 

[willbur]

No, a diode as part of a rectifier network can fail in a way that it starts letting current through imperfectly causing a high ripple. That's why those handheld testers report on ripple. If you have >100mV your car will still likely function but it's an indication you have a diode starting to go. It's a very tricky thing to diagnose and may cause weird gremlins to happen in the car's electrical.

There absolutely are bad rebuild shops. Unless you are hovering over the guy's shoulder you have absolutely no assurance that all the necessary parts were replaced, and of good quality. A unit can be built with crappy parts and still test well electrically or function for a long time. There's dozens of ways that shortcuts can be taken. Using generic voltage voltage regulators is a prime example. If the guy is only charging $100 for a rebuild do you really think he's sourcing an OE regulator which costs at minimum $50??

Good post. Thanks

 

[nobb]

Auto parts suppliers don't make their own diodes!

That's not the point I'm trying to make. I'm simply saying that a rebuilder is probably just going to do a quick multimeter test on the diode and slapping it back in there if it tests good. Rather than replacing the aging pack which would be preferred.

This is just one example. You basically have no idea as to the quality of parts they are using, or if they are even replacing them. And I'm pretty sure the average DIYer isn't going to take apart the rebuilt unit to check on quality.

Will I still use the local rebuilder? Yes a reputable one. But if I'm not pressed for time and I had a choice I'd go with an OE supplier rebuilt (eg. Motorcraft, Bosch, Denso, etc..) unit because atleast they'd be more consistent (theoretically) in their processes, QC, and parts quality. There's this notion that small mom n pop shops are better than the big corporates but IMO I don't believe in that at all.

 

[GMBoy]

Put 2 remans ( Bosch rebuilt in China)on a range Rover last week. Neither worked right out of the box. Found a new few Denso and it charges. New denso was made in Japan.

I had a similar experience a few months back on a 2018 Sport 3.0L - replaced the bad alternator with a AZ reman and it literally started smoking during the test drive and I was afraid it was gonna catch fire. Immediately replaced with a new dealer part and so far so good.

 

[KE7JFF]

Who does even remans domestically? I was told recently from an buyer for an truck shop that even the decent reman outfits in Mexico don't even do a true rebuild anymore and instead if its not an easy reman, they will just break it up for parts and recycling.

 

[f355spider]

Who does even remans domestically? I was told recently from an buyer for an truck shop that even the decent reman outfits in Mexico don't even do a true rebuild anymore and instead if its not an easy reman, they will just break it up for parts and recycling.

The OEMs do. I have purchased Bosch and Nippondenso from car dealers, they were remanufactured by Bosch and Nippondenso according to the box and labels. And here in the USA too...so they have facilities domestically doing it.

 

[Revving2Redline]

Bought a new OEM Honda alternator which is a Mitsubishi. To the right of it is three holes to put a heat shield one to protect which I will need once the cat/downpipe goes bad and I install the high flow sport cat. Some aftermarket alternators don't have those holes for head shield.