The basic problem with using mechanical connectors to join wires is
that there'll always be motion in the connection as the metal expands and
contracts. And with motion, the possibility of intermittency always exists.
When terminals are mated together, there's a contact point or points where
the two terminals touch. As these rub together through thousands and thousands
of thermal cycles, the point of contact becomes worn, dirty, oxidized or
contaminated. The result is either an intermittent or resistive connection
between the two joined wires.
Intermittent connections wreak havoc with digital signals. For example,
dropping a single bit of information from a Ford B/MAP sensor can change
the meaning of the information going to the EEC-IV computer. Resistive
connections are a particular problem when the sensor is of the analog type.
For example, if a 2.5-volt output from the TPS signifies half-throttle,
loosing a volt through the connection means that the computer thinks the
engine is idling when, in fact, it's at a 60-mph cruise. That'll result
in a lean fuel-air mix and a nasty surge.
This exaggerated illustration shows how Stabilant
22 broadens a terminal's point of contact. If the mechanical connection
becomes intermittent, the signal isn't lost because it simply diverts through
the Stabilant. If the terminal halves regain contact, the signal once again
takes its direct path through the contact point, and the slightly more
restive Stabilant returns to having no electrical effect.
And, as we said last month, in addition to wear; age also affects connector
reliability. As a terminal's materials age, the different molecules of
zinc, nickel and copper change their relative positions (called metal migration)
and affect the performance of the terminal. As these materials age and
wear, they're likely to become more abrasive, brittle, resistive and susceptible
Every terminal also has spring-like ability to provide the pressure
needed to keep the co tact points together despite vibration and thermal
movement. The spring effect depends on the sha of the terminal and its
metallurgy.Old terminals may simply loose some of their spring,
and thus become intermittent.
When you pull apart a connector and find that one or more the terminals
inside is bent or distorted, it's time to think about replacement. Crimping
or further distorting the terminal is not likely to result in a good, long-term
connection. Various after-market companies such as NAPA and Wells offer
OE terminal kits that allow you to replace individual terminals in the
connector block instead of the entire connector.
The primary reason for connector blocks is to allow the wiring harness
to be pre-assembled and installed a piece at a time at the factory. The
connectors at the individual components are there to allow these parts
to be individually installed and later serviced as necessary. The point
is that these connectors were never designed to be pulled apart repeatedly.
Leaving them connected and properly mounted is probably the best way to
prevent damage. If you have to pull a connector block apart, be sure to
pull on or pry the plastic body only; never pull on the wires directly.
Although it isn't a very elegant repair, there's no reason why you can't
jumper around a bad terminal in a wire harness connector. Just be sure
to solder the connection on both sides and properly insulate it afterwards.
Again the fix isn't pretty but it does work, and it's not likely to cause
Beyond breakage, the most likely causes of an intermittent connection
are contamination or damage at the point of contact. The key to solving
these problems is understanding what can go wrong and what different treatments
can and cannot help.
If the problem is simply dirt in the connector, any of the various aerosol
electrical cleaners available at your local radio-TV parts house will work
fine. Just spray a healthy dose at the terminals. What you are really doing
is giving the connector a mechanical hosing or flushing.
Some of these cleaners used to contain a mild fluxing agent as well.
The fluxing chemical removed light oxidation, as well as dirt, from the
terminal metal. Because of various EPA regulations, however, these cleaners
are not as available, or as effective, as they once were.
Before using any spray cleaner, make sure that the chemical makeup will
not hurt the connector plastic or anything else the overspray might hit.
Some cleaners have, at various times, contained acetone, xylene, and other
solvents that can eat plastic alive. Its also important that the cleaner
be nonflammable-for obvious reasons.
Besides getting rid of dirt, cleaners are helpful in removing the old
grease from a connector. Connector greases are used to keep dirt and water
out, while providing some lubrication to the terminals themselves. Because
of age and heat, however, these greases can dry out, leaving a thick residue
that actually adds resistance to the connection or prevents it from making
complete contact. Cleaning the dried grease out so that the terminal metal
can flex freely may restore the operation of some terminals.
What spray cleaners do is remove heavy oxidation, fix metal migration
problems, or solve terminal wear. But if you can get at the terminal's
working surfaces, as is the case with some blade-type terminals, it's often
possible to solve these problems by simply working a pencil eraser over
these surfaces a few times. The eraser acts as a mild abrasive that removes
oxidation and smoothes out the tin plating.
Unplugging and replugging the connector also works in many cases, and
there are two primary reasons why. One is that most terminals are plated
with relatively soft tin. When you reconnect the connector halves, the
terminals tend to go back together on a slightly different path. That scrapes
a fresh path through the tin, in effect creating a "new" connection. The
second reason unplugging and replugging works is that the exact connection
points of the terminal are likely to be a little deeper or shallower than
they were to start with. That also creates a "new" connection.
The downside of the unplugging/replugging is that it doesn't often result
in a permanent cure. That's due mainly to vibration and the memory of the
metal. Even though replugging the connection might have solved the problem,
it's possible that through time and vibration, the terminals will find
their old "home" spot. And if that spot is still corroded or contaminated,
the problem eventually returns.
There is one new solution I've tried and been successful with. This
particular fix is a material called Stabilant 22, and its been used for
years in the computer and electronics industries to treat connectors. Stabilant
22 is not a terminal cleaner, but rather an electrically conductive contact
When you apply this watery material to the terminal, it covers the working
surfaces and surrounds the points of contact. If the connection is good,
the Stabilant has no electrical effect. However, a voltage drop across
this material (an indication of a resistive connection) causes it to become
In the case of wear points on the terminal's surfaces, the Stabilant
effectively broadens the point of contact. If the signal cannot flow through
the points of contact, it flows around them through the chemical. The material
does not dry out or evaporate, and will be there as long as the car will.
And its non-toxic, so there's no problem with it's use.
The first time I tried the product was in an attempt to rescue an original
AM-FM radio out of a '69 Chevelle. It had been exposed to the elements
for a long time and the volume and balance controls were intermittent.
New controls weren't available and the usual tuner spray didn't help. I
took the controls apart, applied the Stabilant and the radio has worked
beautifully ever since.
My second experience was with a '91 Plymouth Voyager. In this case,
the fuse for the headlights was intermittent. At night, the headlights
would suddenly go out. Pulling and reinstalling the fuse was all it took
to solve the problem, until it happened again. It is now six months since
I coated the fuse blades with Stabilant, and the problem has not recurred.
I won't tell you that the stuff is cheap, because it isn't. However,
if you use Stabilant 22 at the recommended amount of a drop per terminal,
you might be able to treat a connector for a buck or so. This is much cheaper
than replacing the sensor or wiring harness connector. The maker of the
material recommends that you clean the terminals with a standard spray
cleaner or isopropyl alcohol first, then apply the material.
For more information on Stabilant 22 and where else to get it, write
to D.W. Electrochemicals Ltd., 97 Newkirk Rd. N, Unit 3, Richmond Hill,
Ontario [L4C 3G4 Canada (905-508-7500; fax: 905-508-7502)]
© Copyright 1993, The Hearst Corp. To subscribe
to Motor Magazine, call (516) 227-1411.
Reprint from Motor Magazine - May 1993 by Mike Dale
Eye On Electronics
This month, Mike takes us into the lab to show
how engineers painstakingly design experiments to prove the reliability
of a given product or design.
There's a lot to be said for a good challenge. Some months ago in this
column, I reported on a product called Stabilant 22, which is promoted
as an electrical contact enhancer. I told you that I had used it in several
applications to improve or eliminate electrical interrmittencies in connectors
I also mentioned that associates had used it successfully in computer
applications in which worn or aged connectors were causing loss of bits
and bytes of computer data.
Well, I received a note in the mail recently from one reader who wasn't
satisfied with these claims. Ron Greim, of Budget Jaguar in Orange, California,
wanted to know if there was any scientific evidence proving the stuff really
worked. He also wanted to know if we were endorsing the product. These
are both excellent questions that deserve good, honest answers.
The classic definition of an experiment is to hold all variables constant
except for the one item you want to study. The trick is to come up with
a set of circumstances that can be reliably repeated. Then other factors
can be added or left out to see what the final result will be.
The first step in designing an experiment is to establish a goal. In
this particular case, our goal was to prove whether Stabilant 22 really
improve the quality of intermittent electrical connection.
This first step raised lots of questions:
- How do you deliberately ma an electrical connection intermittent?
- Once you've done that, how do you keep it intermittent from one test to
- Do the conditions that cause the intermittency truly represent what might
actually be seen on a automobile?
- Are these conditions better or worse in cases of high humidity-high vibration
or temperature extremes?
What happens when the metal gets old and zinc migrates to the surface of
the metal terminals?
Is there some type of failure circumstance that you don't know anything
Assuming you've got answers to all these questions, still more question
pop up: For instance, how are you going to measure the intermittency, and
what types of tests and test equipment will be used? And once you've got
the data from the experiment, what are you going to do with it and how
are you going to prove that the results are really the right information
needed to make a rational decision?
Mike's oscilloscope has the capability to record each succeeding
waveform. As you can see, some of the pulses were severely distorted before
Stabilant 22 was applied to the connector terminals.Once the contact
enhancer was applied, the waveform cleaned right up. Repeated efforts
on the vibration table to induce a glitch were fruitless-roof that Stabilant
22 really works!This is all worth mentioning because it shows how difficult
it can be to create experiment to prove the reliability of every aspect
of a given design. When you replace a car part that went bad, what you
are looking at is a failure mode that wasn't tested for, or somehow wasn't
found. You see failures in the field because there isn't an army of test
engineers in the world big enough to test every part under every possible
There are two basic ways to get around the complexity of an experiment.
The first is to limit its size by making the best-judgment "guesstimates"
as to what the likely set of failure circumstances might be. The second
is to make the experiment as practical (real world) as possible.
Over the last couple of years, one of the buzzwords in the automotive
world has been FMEA, for Failure Modes and Effects Analysis. FEMA studies
are used to get around the problem of having to test everything. The design
engineers on a project take a look at all the things that could go wrong
and what the effects might be. They then use this to determine what is
worth testing and how the testing ought to be performed.
A second testing method is empirical, or practical, testing. This boils
down to driving the car up and down the road long enough for something
to break. Warranty failures get all the attention they do because, in the
end, the customer is the real "test engineer".
To keep the Stabilant 22 test down to a manageable size, several assumptions
were made. While these could be argued with, I believe they represent a
reasonable test circumstance.
Because it was handy, a piece of wiring harness from a MGB was selected,
along with the mating terminal from an instrument panel lamp rheostat.
Because Stabilant 22 is to claimed to enhance electrical contact, only
the terminals were part of the experiment. The brass of the terminals was
naturally dirty and the fit not very tight. This setup was chosen because
it represented a connection that could easily be made intermittent.
The rheostat and associated wires were set up on a vibration table.
The table was programmed to shake the connection in a reproducible cyclic
fashion meant to include vibration levels equivalent to a car being parked
and hitting railroad tracks while being driven off, all within a 60 second
For a signal, we chose a square wave voltage very much like what you'd
expect to see from a Hall effect sensor to a computer. The object was to
send the voltage through the wire, through the terminals and out the other
side where it could be monitored by an oscilloscope. The scope we used
has a capture and save mode that grabs and stores what it sees.
The first thing we noticed was that the square wave was getting through
the connection well enough at the beginning. It was only after a half-hour
or so on the vibration table that we found the connection becoming constantly
intermittent (see Figure 1)
The key point to remember is what this intermittency would mean to the
computer. You can see by the extra lines, ragged edges and multiple pulses
that the information represented by this square wave was badly garbled.
What drives most technicians crazy regarding intermittent electrical
problems is that once this garbage passes, it's entirely possible that
the vibration will move the terminal to a new and better position for a
while, temporarily ending the disruption.
Figure 2 illustrates what happened to the waveform after the Stabilant
22 was applied to these terminals. In this case, under these test conditions,
the intermittency went away. And an hour's worth of testing on the vibration
table couldn't bring it back.
There's no end to the tests we could have done under different circumstances,
for longer periods of time or with different types of terminals. Short
of having an array of test engineers at our beck and call, all that can
be said is that Stabilant 22 worked as claimed in the application in which
we used it. While we don't endorse products per se, if we find one that
works, we'll mention it.
Probably the most important thing to get out of our little experiment
is a feeling for the complexity of testing. There isn't an automotive engineer
alive who wants to send anything out into the field that isn't perfect.
But with the level of complexity so high and the available time so short,
mistakes can and, inevitably, will be made. 0--0