What causes alternators to fail??
 

Ok, I'm getting really frustrated here, so I need all the advice I can get. My alternator failed a month ago. I had previously had this same alternator rebuilt at a rebuilder about 3 years ago. So I took it to them again. They said we have have a rebuilt one here ready to go, you just give us your old one. I agreed and paid the $75 and went home to install it. My old alt was a paris rhone, this new to me rebuilt one was a valeo. The install went smoothly and the battery was a getting a good charge about 13.8v.

Anyway, this last thursday, I got in the car to go for a drive and the alternator light was on. I pull back into the driveway and check to voltage at the battery and read 12.2volts and got no change with raising to rpm. I took some time to fully investigate and check the voltage at the starter, same thing. So I took the alt out and checked voltage at the alt wires. ALL was good.

So I hopped in my parts getter and went to the same shop, they remembered me and I said the alt is not working. Their first response was "NO NO NO there is something wrong with YOUR car" :mad: I just about blew a nut! I said absolutely not. I just checked everything, its all fine! They bench tested it and it was giving a good charge. I couldn't believe my eyes. I told them, I know I am not crazy, you need to check it thoroughly. They said call back here in an hour.

Called them back and they said the diodes burned out. So then I asked, why did they burn out? They again gave me the response that it's most likely MY car. They asked if I have a big sound system. I said no. The only electronics I have is the stock stereo, the headlights and the engine. I got home and reinstalled the alt. Everything went back to normal again. Getting a good charge of about 13.8 ish volts. I drove it for a while on that same day of thursday. All is fine.

So I went out of town over the weekend and get in the car when I got back. Guess what! The freaking alt light is ON AGAIN!!! Not even three days!!! Reading 12.2 volts at the battery. Today is sunday, so I can't do anything today. Somebody please tell me what the hell is going on. I cant possibly think of anything that is wrong with my car to cause this. I have not messed with a single thing on my car that is related to the charging system. Is this a case of shoddy workmanship from the rebuilders?

Junk French workmanship....hide it inside the fan shround where it gets really good and hot ( and heat soaks)....throw in some questionable rebuild quality...and then marry that to garage queens that don't get driven very much and put a big "up-take" strain on the alternator ( working its poor guts out to top-off a battery).......

...and ya got your answer as to "why" .....

Wil,
So are you recommending (as you mentioned in another recent post) to go w/ a smaller battery, ie one w/ a lower Ah rating? Can the diodes be "increased" somehow? Obviously, he could drive the car more often, or use a maintainer anytime it is garaged.

Maybe you just need a new battery? If your is almost dead, it could really overtax the alternator every time you start it.

Disconnecting the battery with the engine running can blow a diode. If there is an intermittent connection in the alternator to battery circuit wiring it can be the equivalent of lifting the battery cable with the engine running.

Heat or load issues...killers...oh yeah:

and "mother time"....

Best,

Thanks for the replies so far. My car is not a garage queen by far. It is my committed daily driver. I have not fidgeted with the wiring to the charging system at all. And the battery only a couple years old and starts the car very healthy every time. I'm seriously thinking of getting a bosch alternator and be done with it.

Paris-Rhone? A famous high-quality manufacturer? An incredible alternator state-of-the-art advancer? I don't _think_ so.

"I have not fidgeted with the wiring to the charging system at all."

How did you remove/install the alternator without disconnecting the wiring to the alternator?

Wiring connections (especially Porsche grounds) can loosen/corrode over time due to over heating, vibration, road chemicals and exposure to the atmosphere - they don't have to be"fidgeted with" to fail.

Bosch alternators (now possibly made/rebuilt in Brazil, China or who knows where) can blow diodes too.

Certainly it helps to have a battery smaller in size than the Mercedes-Benz diesel battery ( 88 AH) that normally is installed in mid-80's Carrera's. Then, have a "chipped" battery maintainer when the car is off in the garage ( Schumacher-style float-charger)...that helps too. Don't know if it helps but after a hard run I usually pop the deck lid and let it cool that way. Although LorenB doesn't agree...I run the HUCO brand replacement voltage regulator since it has a much larger heat sink than the stock French piece. Loren says it's junk but it's been serving me well for a number of years now....

Spring for a new Bosch unit. They are expensive but if you are on your third rebuilt unit in three years and still have a problem it would have been cheaper in the long run.