Date: Fri, 12 Mar 2010 07:00:43 -0500
Reply-To: David Beierl <dbeierl@ATTGLOBAL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Beierl <dbeierl@ATTGLOBAL.NET>
Subject: Re: 02 Wire Resistance Questions
In-Reply-To: <4b99bb7b.0d0bca0a.137f.1bab@mx.google.com>
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At 10:56 PM 3/11/2010, Max Wellhouse wrote:
>I guess my questions go like this:
>1. Are there problems soldering extension wires to get the plug to
>reach,or do I find a sensor with wire long enough to get the job
>done? Can I use copper wire or does it ned to be that silver core
>stuff like is on the new and old sensor?
>
>2. Is a full ohm of resistance acceptable or is that part of the "problem"?
Dear Max,
Interesting questions. I wish I had better answers.
1) The "use your existing wire" sensors from Bosch and NGK come with
crimp connectors for the leads. I would not expect soldering to pose
a problem, although from your description of the sensor wire it's
possible there might be. When you say silver, do you mean actual
silver? Silver-plated? Tinned?
Tin-plated? Solid/stranded/woven/insulated-strand woven (Litz)? I
suspect that it's stranded copper, either tinned or tin-plated, and
if so I wouldn't expect a problem using copper to extend it -- I
don't see a reason for them to use anything exotic. However I don't
know enough about thermoelectricity, and the danger I see is creating
a thermocouple whose output could swamp the sensor output. I'd
suggest telephoning Bosch NA and try to talk to an applications
engineer. That may not be possible, but I was once able to talk
directly to a knowledgeable engineer at BASF Chemicals straight from
the main company switchboard, so it's worth a try (He told me,
incidentally, that BASF make the VW house brand antifreeze and did
not understand why VW wanted it phosphate-free, but that's what the
customer ordered and BASF was happy enough to make it for them).
2) This is a high-impedance circuit and wouldn't notice an ohm -- or
ten ohms, or a hundred. However it's a very unusual wire indeed that
would have an ohm in a couple feet, so if you're confident of the
measurement I'm led to think of either something rather exotic or
more likely a damaged/corroded wire. If the resistance measures
different in opposite directions then you've definitely got some
interaction going between meter/probes/wire that either has some
diode effect or is actively generating voltage to screw up the
resistance reading.
Best I can do, sorry...
d
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