Don't solder Oxygen sensor Wire????

I've read a mechanic book. It says on Oxygen Sensor page that
do not solder Oxygen sensor wire because it might cause
misleading the voltage. I'm kind of doubt if soldered wire
would make different voltage reading from unsoldered wire.
How can a soldered wire and unsoldered wire make different
voltage reading? Does anyone ever heard of this or know this is true or
false?

 

Yes, this is called the galvanic effect and is the basis of how
thermocouples are made. Dissimilar metals have a contact potential that
varies with temperature. If the solder is between the two wires, any small
temperature difference will create a voltage across the joint, hence giving
a bad reading. You got good advice.

Dave

 

--------------------------

If you're talking about cutting off the connector half-way from the
sensor, resoldering and heat-shrinking the joints, why not? No salt can
penetrate, like it would on a 'crimp' style.

'Curly'

 

My mechanic says soldering is the *only* way to go, combined with a good
heat-shrink tubing seal.

In fact, he says a crimp connection is far more likely to affect voltage
over time than a soldered connection, because a crimped connection will
attract far more moisture -- and be affected far more by vibration -- than
a soldered connection.

 

Makes sense. Is there not a special kind of solder for situations like this?
There are many different types.

 

Just make sure that you have very good copper-to-copper contact, and
then solder. You won't have a dissimilar metal in the way at that
point, but the solder will chemically and mechanically protect the
joint. This is the essence of good soldering technique. The book is
"right," in that some people (mechanics) just are not electronic techs,
and don't really appreciate the correct way to solder a joint.

 

I checked some online replacement guides. One sensor has stainless
steel wires so it is not compatible with standard electronics solder.
Others recommend soldering.

Stainless steel soldering requires a very powerful flux like phosphoric
acid.

 

Use silver solder and flux. Requires high heat. A BernzOmatic MAPP
gas torch will do the trick.

nb

 

how long do you want this to last? that kind of flux corrodes and eats
the joint, even if you /think/ it's clean. it's /not/ used in
electrical work.

 

but if you read the book further, you'll learn that solder is /NOT/ used
where high thermal cycling is involved, or where vibration is involved.
ask anyone in the aerospace industry - it's all crimp joints in these
applications to ensure reliability. look at your oem honda connections
for that matter.

 

heat shrink helps mitigate the negative impact soldering has on joints
that are subject to vibration, but the solder gives up sooner or later.
same with anything that gets heated. look at the main relay if you
need proof!

your mechanic needs to pay attention to the fact that, crimp is oem,
tested and used exclusively in aerospace because of superior jointing
characteristics, and correct for this application.

he's talking garbage. if there's a proper high conductivity connection,
there's no voltage difference, regardless of connector. the only way
you can have voltage difference is if the connection is interrupted and
there's chemistry going on, but that connection won't conduct a decent
current load.

check under the hood. the earth leads that go from the motor to the
chassis, they're crimped, "open" strand, and last virtually forever. if
you want to test this, replace your own with a lead that has soldered
connectors - it'll be a fun experiment. i've done this before so know
the result, but it would be good to see someone else try it.

 

but if you read the book further, you'll learn that solder is /NOT/ used

True, the crimp joints will outlast the insulation on the wires in some
applications...

I'm assuming that the wire to be soldered isn't in an extreme heat
situation, like right next to the O2 sensor. Also, she should keep her
altitude below 30,000 feet. ; > )

 

He was actually referring to crimps performed by mechanics, not OEM crimps,
with which he has no problem.

And that was his point. Too much variability in a home or garage
connection.

I'm sure you're right, but I think he has a point. I've seen some pretty
crappy crimped connections made by working mechanics. Either the wires were
dirty, the crimp was too tight, or something else was done poorly.

And when the voltage is less than one (rather than being battery voltage),
I can see the probability of errors being higher with a poor connection.

 

But ALL my relays are soldered...?

And if this is the case, why hasn't Honda found a different way to produce
the Main Relay so it won't fail the way it does?

 

mitsuba, the relay manufacturer, probably didn't anticipate the
longevity of the rest of the car! of course it's possible to make a
more durable relay, but how much do you want to pay?

 

i kind of agree, but soldering is no guaranty of quality /and/ increases
propensity to fail due to known issues. so it's back to crimps and
learning how to do it properly, much like any other job.

he has a point about poor workmanship, but that applies across the board.

 

=================================================

Here's a startling factoid about how O2 sensors work . . . . Might have
a lot to say about how we should splice / insulate them. No SILICONE,
(nor silicone grease), and maybe no heat shrink.

Borrowed from
http://www.autotap.com/articles/Understanding_Oxygen_Sensors.html
-----------------------------

Older style oxygen sensors actually have a small hole in the body shell
so air can enter the sensor, but newer style O2 sensors "breathe"
through their wire connectors and have no vent hole. It's hard to
believe, but the tiny amount of space between the insulation and wire
provides enough room for air to seep into the sensor (for this reason,
grease should never be used on O2 sensor connectors because it can block
the flow of air). Venting the sensor through the wires rather than with
a hole in the body reduces the risk of dirt or water contamination that
could foul the sensor from the inside and cause it to fail. The
difference in oxygen levels between the exhaust and outside air within
the sensor causes voltage to flow through the ceramic bulb. The greater
the difference, the higher the voltage reading.

'Curly'

 

I think this refers to the portion of the wire that's right at the sensor
body. I'm not sure it would make much difference if you had a piece of
heat-shrink a foot away from the sensor.

 

It's not through the individual wires. It's the gaps between the wires
in the harness.

Older sensors had the wires exiting through a tight rubber seal. Newer
sensors have the wires exiting from a loosely crimped sleeve.

 

==============================

Nope, because it gets it's air way up higher, where the connector is.
Water would run DOWN the wire and contaminate the sensor, if it breathed
from the bottom end. Now I know to never put SILICONE anti-corrosion
paste in an O2 sensor connector for that reason. I love that stuff, and
surely would have used it if I hadn't read this article.

'Curly'