Date: Wed, 30 Jun 1999 19:26:16 -0500
Reply-To: cdo9@CSI.COM
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Cliff Ober <cdo9@CSI.COM>
Subject: Re: Generic, three wire, O2 Sensor choice for digifant?
In-Reply-To: <e930e214.24abf388@aol.com>
Content-Type: text/plain; charset="us-ascii"
Ken,
Since I been trouble-shooting my own van's fuel and electronics systems I've
been watching the O2 sensor output. Between what I see and what Darrell
Boehler has advised me, the voltage levels on the Vanagon's O2 circuit are
normally around .5 (one half) volts, plus or minus about .3 volts as it
fluctuates. That's a thousand times higher than the microvolt levels you
said you were advised to be found in such a circuit. I find it very hard to
believe that a few milliohms resistance in a splice joint can cause any
problem at those voltage levels.
I CAN believe however that a long run of unshielded wire to the sensor could
pick up ignition noise and perhaps cause a problem. I made a stupid error
when I replaced the O2 cable's connector on my van. Not realizing the wire
in the harness was shielded, I just crimped a new spade terminal on and
shorted it out. VW brought shielded wire out from the ECU connector, but it
ends just a few inches outside the harness. That leaves about a 15-16 inch
run over to the O2 sensor that's unshielded. It would be easy for ignition
or fuel injector switching impulses to be picked up by that long wire run.
There may not be any problem with it, but who knows? Ideally, shielded wire
should probably be used all the way out to the sensor, but of course that
means more complicated connectors to the harness to accommodate two
conductors.
Cliff Ober
-----Original Message-----
From: owner-vanagon@GERRY.VANAGON.COM
[mailto:owner-vanagon@GERRY.VANAGON.COM]On Behalf Of KENWILFY@AOL.COM
Sent: Wednesday, June 30, 1999 5:26 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Generic, three wire, O2 Sensor choice for digifant?
This is a subject that I have been thinking about and also talking to others
about for a while. Talked to a guy that runs a business selling Catalytic
Convertors and also Oxygen sensors. I asked him if splicing the three wire
oxygen sensor was a good idea. He said "No" because the ECU is looking at
microvoltage inputs from the Oxygen Sensor and a butt splice would cause a
resistance (although a small one) that would make the ECU get false readings
(he called it a "lazy" oxygen sensor). He said maybe a solder splice would
be acceptable, but I have seen most folks idea of soldering and it ain't
pretty (leave this to the pros). He said that he only sells direct plug in
oxygen sensors for this reason. He was not financially motivated in telling
me this since he didn't have any 3 wire Vanagon oxygen sensors to sell.
This
was merely his experience.
So does anyone else have an opinion on this one? I mean I would love to
sell
the cheapy universal 3 wire sensors but not if they are going to cause
performance problems or loss of mpg in a customer's van. The price
difference is quite a bit though. The universal (u-splice-it) is $30 while
the plug in oxygen sensor is normally $120 (however I have a special on it
for the next couple of days for $100). I would actually make more money
selling the universal one but, as I said, I just don't feel comfortable with
this.
Ken Wilford
Van-Again
John 3:16
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