Electrical gremlins again

[Radek]

Tony,

The charging light (red with the image of a battery) comes on.  It looks like replacing the ignition switch solved the flickering/dying lights problem.  I just can't understand why the system would charge with the old, weak battery and not charge with a new/strong one.  Tomorrow I'm going to put the old battery back in and see what happens. And, of course, check/clean all connections that I can get my hands on.

Radek.
  ----- Original Message ----- 
  From: Tony Lum 
  To: Radek 
  Sent: Tuesday, May 25, 2010 9:16 PM
  Subject: Re: Electrical gremlins again


        Radek,

        When you turn the key to the "ON" position, the battery (alternator) light better go on.  The light connects to the D+ terminal on the alternator to provide startup power to the rotor field coil.  Without this, the alternator will not charge.  If it is not charging, put a voltmeter on the D+ terminal (the small one) you should have +12V there.  If not, check for corrosion in the ring terminal or it may be a broken wire back to the instrument cluster.

        HTH,

        Tony
        '83 ur-quattro
        '87.5 coupe GT Special Build
        '01 A4 Avant quattro 2.8

        --- On Tue, 5/25/10, Radek <radek at istar.ca> wrote:


          From: Radek <radek at istar.ca>
          Subject: Electrical gremlins again
          To: quattro at audifans.com
          Date: Tuesday, May 25, 2010, 5:47 PM


          Hi Guys;

          My son's 1988 90Q is acting up again.  I took it to work this morning, stopped at a gas station, filled up, tried to start it. It would crank but not catch.  I turned the key back, then to "on" again and all instrument lights started flickering, then died completely.  I turned the key back again, then back to "on" and everything was back to normal.  Tried to start it but the starter would just click once and not turn.  Another try - everything dead.  This went on a few times so I figured out a busted ignition switch.  Got the car push started when the switch was kind enough to provide a good connection and eventually got the car home - voltmeter would show a bit low, 13V while underway.

          Back at home I changed the ignition switch to a brand new one (had a spare one he shelf).  The old switch had the typical broken plastic collar, so I thought I was OK.  NO, NO.  The flickering was gone, but starter would not crank.  When turning the key to "start", voltage at the battery would drop to 6V.  OK, in addition to a broken ignition switch the car may have had a shorted battery.  

          I put in a new battery (had a spare one on the shelf), fully charged, and tried again.  Key turned to "on" - everything seemed fine.  To "start" - cranking, and finally the engine runs.  I look at the voltmeter and THE ALTERNATOR IS NOT CHARGING.!  WTF?  It was charging before, with the shorted battery and a broken ignition switch!  Voltage at battery with engine running was showing 12V.

          I put in a spare voltage regulator (had a spare one on the shelf) and it still isn't charging!

          Where to look next?  

          Radek, Ottawa
          _______________________________________________
          quattro mailing list
          http://www.audifans.com/mailman/listinfo/quattro
          http://www.audifans.com/kb/List_information