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

[Ernie Stephens]

Josh,
I have been having similar issues with the warning lights coming on intermittently or glowing dimly. I took my car in for service yesterday and had them top off everything and it seems to have solved the problem.  I don't know if the warning lights share a common ground or if there is a leak (faulty diode) or if it was just a coincidence but you might just want to make sure that all of the reservoirs (even the windshield washer) are topped off.
Good luck,
Ernie
---- Original Message ----- 
  From: Josh Allen<mailto:heyallen at null-ptr.net> 
  To: dan at landiss.com<mailto:dan at landiss.com> ; Mercedes Coupes Mailing Lists<mailto:mbcoupes at mbcoupes.com> 
  Sent: Wednesday, February 24, 2010 11:31 PM
  Subject: Re: [W126 Coupe] Strange gauge lights error, any ideas?


  Markus,
  After testing today, it's sitting at 13.7-13.9 at idle, and 14.2 or so at ~ 2k rpm.
  I was reading the same voltage indicated at the terminal block on the fender, the battery positive terminal, and the B+ terminal on the alternator.

  Looking in the charging system section of the ETM, I'm going to hook my oscilloscope to the B+ terminal of the alternator and see if it has an abnormal ripple, and failing that, I may just wander down to the Napa and see what they can tell with their analyzer.  It's still under warranty for most of another two years.

  The fuse on the top of the OVP was still good, I double checked, as well as having the OVP apart to clean up it's pcb which had some nasty flux residue or corrosion on the solder side of the board.

  (FYI: The alternator that is currently installed is PN:  RAY 2138381    http://www.napaonline.com/Search/Detail.aspx?R=RSE2138381_0218228923<http://www.napaonline.com/Search/Detail.aspx?R=RSE2138381_0218228923>  with a 72 month warranty.)

  -Josh




    On 2/24/2010 2:45 AM, Markus Meyer wrote: 
    Josh,

    I'd start by checking battery voltages, resting (car not on) and with car running (this shows your alternator voltage), and go from there. Any idea what alternator was put in, where it came from, was it new, rebuilt, new regulator used, etc?

    Once you rule out a charging problem, you can move on to other things like the OVP.

    Markus

      Markus,

      The new alternator was whatever I could get from the Napa warehouse store, since that was the only alternator available on short notice at the time.  
      It had a new regulator with it, and at the time was putting out 14.5-14.7v when running, but I don't know currently.

      I'll check up on the charging system today, one way or another, I just couldn't when I found it yesterday evening.

      Thanks,
      Josh




  Dan, 
  The dim light is while the car is running, but not revved above idle.  Once I rev it up at all, the lights all glow brighter, in sync with each other, but with the battery light the brightest at all times.



  On 2/24/2010 7:55 AM, Dan Landiss wrote: 
    Josh, could you clarify for me me whether the dim lights are BEFORE you start the car, or immediately AFTER? I recall some really crude method of distributing the grounds behind the instrument panel.

    on 2/24/2010 9:44 AM Josh Allen wrote: 

          When I start the car, the charging system indicator glows dimly, as well as the brake wear light and the empty fuel system light, but both of the latter lights are around half the intensity of the charging system light.

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