8 cylinder front engine iconic vehicle
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By Majestic Moose
My car keeps killing alternators. It is easy to blame the alternator if one or two fail but with a third it might be something else.

First a little history. When I bought the car the PO had replaced the alternator and it never performed well, it turned out to be a 75A unit from an 80's Audi with no back cover or cooling hose mounted. Actually this one never failed but it does not provide enough output.

I bought and installed a used correct alternator, it worked okay but it was noisy so I knew it would not last long. It also need a rev around 2500 RPM to kick in.

I replaced it with a Bosch 325x and fitted the back cover and cooling hose. It worked great.. for one day, about 50 miles.

The used unit went back on. It finally failed while driving. On removal I saw it was the diodes destroyed.

I installed another Bosch 325x, this one worked great for exactly two months and failed on my way back from Frenzy. This time I noticed the volt meter at 11v after a redline run in second gear. I was thinking maybe I over revved the alternator but my pulleys appear to be the correct sizes.

Everything on my car has been gone through. I have no current draws; I can park the car in November with the battery connected and no charger and it will start right up in Spring.
All bulbs are LEDs but I do have an electric radiator fan setup that only runs when needed. It pulls 17A.
The battery is a beast of a Bosch AGM. It is from 2016 but holds its charge and I was able to drive 60 miles with AC and lights on and it was still at 12.3v when I got home.

So I am at the end of my patience and willing to consider other options. I can replace this one for free under warranty but I am starting to think there might be something causing these alternators to burn up. For now I cannot figure it out, any ideas?
Last edited by Majestic Moose on Mon Sep 27, 2021 8:42 pm, edited 1 time in total.
By JBRob007
Front of engine (FOE) wiring harness is where i would start. It’s the beginning & end of most mysterious issues. Talk to Sean Ratts.
By Mrmerlin
I know you said all bulbs but did you change the not charging warning lamps to LED
Take the failed alternators to the re builder shop let him figure out whats failing
By Majestic Moose
Those little bulbs I left stock. When I had the cluster apart I tested the resistor and the bulb does work.
For now I will replace it, the battery, and the ground straps. Other than bad luck I cannot figure it out.
By Mrmerlin
yes take it to your local alternator re builder otherwise you might have a 4th
I have a good guy in Glenside, Harry Halco alternator repair.

Phone: +1 215 884 0946
By Majestic Moose
I am not sure I follow. Roger is kindly sending me another one.
Should I take it to be rebuilt?
By Mrmerlin
at this point you have no Idea why,
and swapping more than 2 alternators should make you want to know why unless the labor/time is free
By Majestic Moose
I switched out the alternators this weekend. The new one is working as it should.
I expected to see burnt diodes on the old but everything looked fine and tested good. I could hear a faint clicking when spinning the pulley at regular intervals at the back so I removed the voltage regulator and found a broken wire on the rotor.

There are two of these connections, the other side is fine.

It seems like an easy fix to resolder the connection. I may do that, get it tested that it works and keep it as a spare. Roger I would pay for the second alternator.
By Mrmerlin
Well thats nice easy fix,
and you learned something to boot,
and you shared your wisdom with us,
thank you !

NOTE it also appears that the good wire from the rotor has a notch on it ,
and thus could be hitting something inside the housing see that flat spot.

NOTE its been painted and the paint is still intact might be worth more investigation.

The biggest issue I have with alternators are the fitting of non stock VRs,
and this pertains more to Paris Rhone,
but I have seen a few Bosch alternators with funky operation.
On the PR alternators with aftermarket VRs the voltage seems to be OK for a bit,
then once the unit gets warmed up the voltage spikes and runs at 15V output,
this will quickly cook the battery.
Non Bosch parts like Huco simply stop working,
I have to figure this is from putting the alternator into service with a low charge battery,
] this makes the new part run very hot and cooks it.

Most VR issues stem from worn brushes and replacing them will fix them.
NOTE also inspect the slip rings if they are worn or grooved,
they can be cut down some or removed and new ones epoxied inplace.

Glad your machine is back online.
By UKKid35
Mrmerlin wrote:Non Bosch parts like Huco simply stop working,
I've bought a Beru VR, is it worth fitting or should I discard it?
By Mrmerlin
I would get a Bosch regulator if you only want to do the job once.
Otherwise try the beru if it works then great
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