[W126 Coupe] Strange gauge lights error, any ideas?

[Josh Allen]

If I were going to have to pay for the replacement, I'd definitely be 
looking for an AL129X alternator to swap in, but it's still under 
warranty so it's just going back to Napa.  They said they'll have one 
for me tomorrow, I just need to bring in the failed one and the receipt 
for it.

-Josh

On 2/25/2010 1:38 PM, Markus Meyer wrote:

> Suggestion, as I just went through a similar test.  I have several 

> 126's, so I just stole the alternator from my SEC to keep my wife's 

> SEL going, since the SEC is hibernating right now anyway.

> I about to get a Bosch AL129X alternator from the yards, found on late 

> 80's, early 90's SAABs.  Same housing, 115 amps vs. 80 amps.

> I've been told most rebuilds are junk, so just be aware.  Dealer wants 

> close to $350-400 for one!

> Markus

>

> On Thu, Feb 25, 2010 at 4:35 PM, Josh Allen <heyallen at null-ptr.net 

> <mailto:heyallen at null-ptr.net>> wrote:

>

>     Ok, I think I've found the issue.

>

>     I followed the suggestions of the ETM and a few others here,

>     tested the resting voltage (12.3v), idle voltage (13.7v), and

>     voltage with various electrical loads on (13.4v).  I then ran up

>     the RPM with the loads (13.9v max), and without (14.2v max).

>

>     I then hooked up my oscilloscope and checked the B+ waveform, as

>     the ETM suggests, to look at the condition of the rectifier bridge

>     inside the alternator.  It came up with an obvious missing phase

>     in the waveform, so it appears that one of the diodes has failed.

>

>     I've attached a pic of the waveform on the scope, for those who

>     might find it of interest.

>

>     Thanks for all the suggestions, now I get to do battle with the

>     parts house!

>

>     -Josh Allen

>


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