Our local electric motor shop stopped repairing alternators a few years ago. They couldn't afford the warranty claims. The biggest issue was voltage regulators, but they had bearing problems as well.

Obviously OEM's have better quality control, even if they come from China.
I would take a used one out of a low mileage wreck over any clone or rebuild.

My choice was brand "B" for a couple of other reasons, including the summary of this reliability poll.

My first plane power failed after 100 hours no additional cooling. It was replaced under warranty by an other one and I added a cooling hose. Failed after 150hours.
Replaced with an other unit last week... let's see...

$32.11 free shipping
 

https://www.amazon.com/Stator-Leads-.../dp/B07HFGR9PR

Ensure movement of stator inside housing and of 4 stator leads are eliminated with high temperature sensor safe silicone. Unipoint and PP should have been ensuring this on their $500+ alternators. Its easier to blame out of balance props and lack of cooling blast tubes. DIY or take your airboat alternator to one of the few remaining alternator shops and spend 1/6.

Stator

Replace OEM(s): Denso

For: Nippondenso

Used On: Denso Alternators

Amps: 60 Amps

Amps Draw: 58 Amps

Amps Low Output: 60 Amps

Condition: New

Lam Stack ID: 3.031in / 77mm

Lam Stack OA Width: 25mm

Lam Stack OD: 3.937in / 100mm

Lam Stack Thickness: 1.051in / 26.7mm

Mounting OD: 100 mm

Slots Count: 36 Slots

Specification: 77X100

Voltage: 12 Volt

Weight: 1.66 lbs / 0.75 kg

About 8 years ago I switched from the Van's 35a alternator to a Nippondenso, the one for a 70's Honda. I wired around the built-in regulator and retained my B&C external regulator. I had 2 failures caused by broken stator wires (covered by warranty). I stabilized the stator and the wiring as mentioned in the previous post and it's been fine ever since.

Question about the guts . . .
 

The stators have a shoulder bolt that secures them to the housing. Are they loose? PP uses 2 of them but the design allows 4 to be used. More likely it is rotor orbit or rotor balance that initiates the vibration. Or the bolts were not properly torqued. I found a screw protruding from the belt end bearing retainer on one. It just was not screwed all the way in. A QC issue to be sure.

Question to you guys, what did the SRE (slip ring end) bearing look like? Did it have two plastic rings embedded in the outer race?

Yes, mine were loose. Star washers now installed.

I haven't read every post, but...
 

regardless of the reasons for failure, there are enough respondents to the OP to say with some level of confidence that:

Out of all respondents reporting failures before 250 hours,
[*]Automotive Alternators failed at a rate of 28/148 or 18.9%[*]Plane Power Alternators failed at a rate of 58/201 or 28.9%[*]B & C Alternators failed at a rate of 3/116 or 2.6%

Based on this survey, why would anyone buy a Plane Power alternator?
After that, I'm left with a choice of an automotive alternator that costs less than $100, is lifetime warranted, and has about a 1 in 5 chance of failing in the first 250 hours or,

I can buy a B&C (without a lifetime warranty?) for about 8 times as much,
knowing that the odds are very good that I'll make it past 250 hours without having to do a changeover.

I see that many respondents listed the time that they got out of their hardware before failure. This is a useful survey. Too bad everyone didn't list time to failure - that would have given us more useful information for decision making.

BTW, I'm now on my fourth automotive alternator, with total airframe time around 1300 hours. If I had a little extra cash laying around, I'd switch to B&C - my failures always seem to occur when I'm on an instrument FP and out of state.

Terry, CFI
RV9A N323TP