Date:         Thu, 16 Oct 1997 09:30:07 -0500
Reply-To:     "Rick Sherrod (hopeless VW nut)" <kdf_cars@MYLINK.NET>
Sender:       Vanagon mailing list <Vanagon@Gerry.SDSC.EDU>
From:         "Rick Sherrod (hopeless VW nut)" <kdf_cars@MYLINK.NET>
Organization: Specialty Automotive
Subject:      Re: 02 mixture questions
Content-Type: text/plain; charset=us-ascii

Tom Young wrote:
>
> On Wed, 15 Oct 1997, Rick Sherrod (hopeless VW nut) wrote:
>
> > >>>rom:    db25 <Douglas_M_BENSEN@UMAIL.UMD.EDU>
> > Subject: O2 mixture questions
> >
> > >>>I have several questions when it comes to adjusting my mixture using the
> > oxygen sensor.
> >    >>>     1. Do I have to disconnect the sensor with the engine off?  The
> >            computer will have a memory if I don't.  Does it matter?  Can I
> >            leave the sensor connected to the computer to read the voltage?
> >            [snip]
>
> > You should be able to set your mixture just fine while
> > connecting/disconnecting 02 sensor while engine is running.
> > [snip]
>
> > Questions/comments?
> > Rick Sherrod
>
> The Bentley (and others) are very definite about having the ignition OFF
> when connecting/disconnecting the O2 sensor, not that that means they're
> necessarily right.  How are you so positive that it's OK to
> connect/disconnect the O2 sensor with the engine on?
>
> ---------------------------------------------------------------------
> Tom Young               young@sherlock.SIMS.Berkeley.EDU
> Lafayette, CA  94549    '81 Vanagon
> ---------------------------------------------------------------------


Tom,

I may be wrong, Tom.  I've been wrong more times than I care to admit.  If you feel more
comfortable following the Bentley manual, continue by all means.  I don't presume to
change the way other skilled Mechanics work.

I wasn't quoting from the Bentley.  I was giving advise based on my experience and the
knowledge that the 02 sensor circuit operates on voltage supplied solely from the sensor
itself, not from the computer.  The computer only monitors the voltage present.  This
assertion from VW/Bentley may be there as a disclaimer to keep folks from hurting
themselves in a running engine compartment or maybe to avert a voltage "spike" when
connecting/disconnecting.  However, on a circuit that tops out at about 1-2 volts I fail to
see where a voltage spike would originate since the circuit without an 02 sensor installed
carries absolutely no voltage or current.  These computers are also much sturdier than
they are given credit for in my experience.  These computers also don't set fault codes or
remain in fail safe mode when 02 sensors are reconnected, so no odd conditons exist
after 02 dis/reconnection.  If you have information about this that wasn't covered here
please let me know as I am still always learning (the day that I don't learn something is the
day they cart my sorry carcass to the morgue).

As a VW Audi mechanic I apprenticed my 30 year VW tech Father for seven loooong
years.  Now I'm on my own as a dedicated VW restorer.  I find it much more enjoyable to
fully restore a VW than to just do what some financially strapped owner can afford to do
on a weekly salary.  Too many of the customers from our old shop would limp around in
their poor little VWs for years and when they landed a better-paying job they abandoned
their trusty VWs and bought fancy late-model Toyotas and Hondas & such, their old
restorable VWs would go to even poorer weekly wage earners.  To someone who loves VWs
the way I do, it is a heartbreak to watch cars be run into the ground like that year after
year.  I enjoy restorations & selling my work as completed VWs much better.

Thanks for dropping me a line, Tom!

Rick Sherrod
Macon, Ga
'82 Vanagon mutt
'81 Audi 5000 Diesel 5spd
'88 Fox 4dr 4spd