Alternator...fried...twice?

[CLS70]

Hi

A couple of weeks ago, got the Red Battery alarm "Charging System Malfunction"), shortly after car battery died, all sort of error messages but I knew it was electrical related.

Went through troubleshooting (checked Battery, Ground Straps replaced,...), managed to confirm alternator (180A Bosch) was out.

So installed NEW alternator, fire up right away, car worked fine, charged battery and displayed 13.5-14.2 V when running, all error messages went away; took it for a spin and then suddenly died again....same error.....no more charge....

So got a replacement unit (NEW), re-installed, replaced belt tensioner, belt and idler pulley. All worked fine for 5 days, no issues, then suddenly, "Charging System Malfunction" again, and voltage dropped to 11.5v (when running), measured at alternator, same value......

What are the odds of having failure of two new alternators.....what am I missing?

Have checked connections and fuses but can't find anything wrong but definitely there should be a reason for the failure.....any ideas?

[andrewwynn]

It happened to me!

Also Bosch

O'Reilly let me trade the second one in for the valeo for the price difference vs.(all under warranty.

On the m54 there was supposedly a situation where the oil sensor could short out and take out the alternator but when it went back to valeo it lasted the rest off that car's life

[CLS70]

Thx - will check if I can get a Valeo but still trying to see if there could be a hidden issue somewhere else.

When thinking about the driving conditions when the new alternators failed, the only common factor was high RPM...e.g., got the errors/failure after revving up.....

[740iS]

Even though the case may be Bosch or even Valeo, if it is a rebuilt from an auto parts store it is NOT a Bosch or Valeo. They use generic rebuild parts and they do not play well with BMW systems.

Do yourself a favor, get a NEW Bosch or Valeo. Preferably Valeo as they were the OE builder for the E70.

I went through this very issue on one of my E70's with "rebuilt" Valeo alternators from Autozone. Replaced multiple times. Finally bought a new Valeo and all those problems went away. And lucky me, I had to argue with Autozone for a refund and finally got it.

[andrewwynn]

The price was barely different for new vs. rebuilt I think I had to pay like $25 to go from rebuilt bosch to new valeo. Def pass on the rebuilt from auto parts store as mentioned using cheap VR parts is the problem

[Zulu95]

I read a thread about these AZ rebuilt units being processed south of the border and the process being solvent dip to removed oil/grease, lube the bearings and a quick respray then into the "REBUILT" box. Given the number of rebuilt disaster threads over the yearfs I can see this being an accurate description of the process. One guy put 3 AZ units into his E53 and paid his indy each time for the pleasure. Number four was a nice new Bosch.

[CLS70]

so returned the rebuilt one, got a new Bosch (same specifications as the unit I had originally - 180A), installed and so far no issues (note the rebuilt one lasted 2 weeks...) so will monitor closely.

installed two new ground straps; new belt, pulleys and tensioner....will see how it goes..