Electrical gremlins again

[Radek]

Thanks to all you guys for putting me on the right track.  So far, I replaced the ignition switch (old one was broken), and the battery (old one would drop to 8V when the key is turned to run).  I cleaned terminals at the alternator, the starter and the jumper strip in the relay box, and replaced about a foot of wire at the solenoid (old wire had corrossion, white powder was falling out from between the strands of aluminum).  I also added an extra ground between engine block and the chassis with a heavy gauge wire (thickness of your little finger).  
Car started five times in a row, so far.  

What worries me, though, is that while there is 13.8 V at the alternator when charging and nearly the same (like 13.78) at the battery, the voltmeter fluctuates.   Car idles at about 900 to 1000 rpm (too high, I know, I'll get to it next).  At 1000 rpm the voltmeter needle is fairly steady, there is just some barely visible vibration. However, when rpms drop, the needle (sometimes, not always) goes crazy, jumps up and down.  Could that indicate a charging problem that could have killed the old battery?

Radek


--- 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
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