Electrical gremlins again

[Andrew Dickinson]

Also, the 'crazy needle' syndrome would indicate a short or open wire issue to me if when it drops it is below the battery voltage.  For the short you may be able to follow your nose to burnt wire.  For either instance it appears to be intermittent so banging the car in different places may prove fruitful to narrow down location as well.  HTH.


--- On Wed, 6/2/10, Cody Forbes <cody at 5000tq.com> wrote:


From: Cody Forbes <cody at 5000tq.com>
Subject: Re: Electrical gremlins again
To: "Peter Golledge" <petergolledge at gmail.com>
Cc: "Radek" <radek at istar.ca>, "<quattro at audifans.com>" <quattro at audifans.com>
Date: Wednesday, June 2, 2010, 7:44 AM


You also might want to check for AC current with a multimeter. Failed  
diode(s) can put AC current into the system and give all sorts of  
funny issues. There will usually be a minimal amount, like less than 1  
volt, anything more than that is no good.

-Cody (mobile)

On Jun 2, 2010, at 12:57 AM, "Peter Golledge"  
<petergolledge at gmail.com> wrote:

> Since the battery _should_ act like a capacitor I think you still have
> either intermittent ground or positive battery terminal to see large  
> voltage
> swings.  Since you don't mention below check/clean the battery  
> ground cable.
> I had a loose one of the those drive me nuts in a 5000.  Not sure if  
> the
> smaller audis had the dreaded "splice" in the positive cable at the
> footwell, others would have to comment on that as a possible cause.
>
> As for the source of the surging voltage I'd suspect a voltage  
> regulator,
> they can be replaced with the alt in place and the they are relatively
> cheap.  You might want to pull the regulator and check the brushes  
> as well
> as the regulator ground to the alt.
>
> -----Original Message-----
> From: quattro-bounces at audifans.com [mailto:quattro- 
> bounces at audifans.com] On
> Behalf Of Radek
> Sent: Tuesday, June 01, 2010 8:27 PM
> To: quattro at audifans.com
> Subject: Re: Electrical gremlins again
>
> 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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