Best method of how to safely and accurately test for faults with a vehicles and
connectors and how to fix them so can get back on the road in no time when
attempting to diagnose the causes of an electrical fault on a vehicle check
wiring well that’s all well and good buy it doesn’t mean you should just give its
once over a few taps it also involves checking the electrical integrity of the
wire and qua of its connectors and terminals while these might seem simple
enough doing them incorrectly can mean potentially damaging the sensitive
electrical systems that keep modern cars running but before we jump right
into the do and do not of diagnosis let’s quickly have a closer look at the
anatomy of wiring and connectors in an automotive electrical system all the
wiring in a vehicle will be made up of multiple tiny copper strands surrounded
by an insulating thermoplastic layer the copper acts as conductor of the
electrical current traveling from the battery and the outer layer protects these
strands from heat moisture and from shorting to any other conductive material
multiple wires are usually needed for various components within a vehicle so
for organization they are grouped together in looms and at the end of these
looms are connectors which join sections of wire together inside these
connectors individual wires are Attached to terminals which act as the end
points of the wires and connect to corresponding pins on a plug providing a
secure connection now the major things that can go wrong with wiring is
damage to the insulating protective layer surrounding the copper strands in an
automotive system heat and vibration can wear  this protective layers down
and cause moisture to get into the copper strand causing a high resistance for
the electrical current going through the wire this cause all sorts of the
problems with the electrical components on a vehicle and can something very
difficult to see with a naked eye especially when looking at thick wiring looms
that snake here there and everywhere this is why it is important to know how
to properly test the electrical integrity

How to back probe ?
Probing back probing involves using a multi meter equipped with a pin or back
pin probe and inserting it next to a wire on the rear of a connector in order to
investigate the wires integrity this testing method is king in automotive
diagnostic world as it doesn’t risk any damage  to the wires insulating layer or
terminals and you don’t have to remove any connectors to carry it out this is
terminal and  don’t have to remove any connectors to carry it out this is
terminals which can be from multiple different systems within the vehicles so
live testing with everything powered up and connected is a lot easier to carry
out an effective back probe test you will first need to remove the back cover
from the connector to expose the rear of the effected wires terminal then with your PIN probe attached to your multi meter carefully Slide the probe down
the side of the wire ensuring it does not damage the wire insulation or any
other weatherproof seal the pin will usually be able to be inserted further at a
certain point due to the orientation of the terminal within the connector so it is
worth trying to ins the probe at least two point on the side of the wire to
determine where the terminal if you want to carry out a back probe test on a
working wire first in order to properly determined the orientation of the
terminal on the connector so the suspect wire

Diagnose a faulty wire .
The technique to identify what kind of fault is affecting a suspect wire these
can usually be categorized into 3 main circuit failure a short an open or high
resistance high resistance is usually caused by corrosion of the internal
copper strands poor terminal contact or overheating damage to the wire
caused by high current draw to test for this turn your multi meter to ohms and
check the continuity of the suspected wire for a standard 12 gauge automotive
wire the resistance should be less than one based on the assumption that it
should have a resistance of less than 0.026 ohms per meter of the wire
another way of diagnosing high resistance in a wire is to conduct a voltage
drop test this is especially beneficial when diagnosing damage to a wire
caused by high current draw and it is a better way to test for resistance
because you are testing with everything powered up and functioning up to do
this ensure the vehicle is running and you have the battery under load by
turning accessories on such as the air-con and radio turn your multi meter to
volts DC and back probe either end of the wire at each connector you
shouldn’t see more than 0.2volts on most automotive 12 gauge wipes but it is
worth consulting your manufacturer specifications before condemning the
loom an open circuit can be diagnosed

Diagnosed an open circuit .
Resistance reading you will see or open circuit on the multi meter these faults
are caused by complete break in the wiring caused by a complete break in the
wiring caused by severe corrosion damage from an external overload or from
general tear and wear over time the other causes of an ope circuit could be
due to poor terminal

Diagnose a short circuit .
Different circuits touch each other directly causing the electrical current to flow
through a different path then intended and resulting in a surge of electrical
current they can occur either when a damaged live or current carrying wire
makes contact with a a=damaged ground or low reference wire which is called
a shatter ground or when one current carrying wire makes contact with
another out of the intended circuit path which is called a short to voltage to
test for a short in an automotive circuit you should set your multi meter to volt
DC and back probe the affected wire and test it against either a known good
ground or a supply voltage depending in the wire in question if you get a
reading outside of the desired range then isolate the suspect wire from the
rest of the circuit and retest in this example set you multi meter to ohms and
perform a continuity test between the native side of the battery and the
affected wire has been removed from the terminal there should be no
continuity between it and the battery ground so if there is any resistance
displayed then you can assume the wire is

Repaired damaged wiring
Cut out the damaged section of wiring bear in mind that every time you cut
and re join a wire you are creating a potential point of weakness for ingress to
enter to ensuring you are properly repairing any damaged is pivotal there are
method to rejoining a wire but started by cutting each side of the damaged
wire using precision side cutters to get a clean cut and then strip each end of
the wire using appropriate sized wire strippers now this is where the methods
of repair differ and these can be affected by the amount of sack you have with
a wire or the space you are working with a crimp sleeve is the easier method
two important things to remember when using there are one use a good
crimping tool such as ratchet crimp-er to ensure the connection is solid and
even and two always use a heat shrink cover as a crimp sleeve is not other
method is to repair a broken wire which we would recommend is to solder it
back together the important thing here is to make sure you are twisting the
wires together tightly to create a strong joint then apply the soldering iron to
the joint followed by the solder and allow to flow all over the connection this
will create a joint which has a solid and reliable

Repaired damaged terminal .
Element now damaged wiring is only one half of what can be faulty within in a
wire the second thing to check for is terminal tension and connector corrosion
the corrosion is fairly simple to spot just remove the connector and visually
inspect both ends for any crusty build up discoloration terminal tension tests
involves a little more know how and the correct tools so before you start you
will need the correct size terminal drag tool for the connector For reliable
reading insert the drag tool into the affected terminal and slowly pull it out
there should be a noticeable resistance as you remove the terminal tension is
good if the tool is removed easily or it has noticeable amount of wiggle room
then you will need to replace or re tension the main steps are same so start
by removing the connector from the corresponding plug if you have not done
so already remove the back cover of the connector to expose the back of the
wires this may requires removing the locking mechanism especially on large
connectors then remove any secondary lock or terminal position assurance
device from the front side of the connector to expose and free up the terminal
Different connectors have different sizes terminals with different locking
mechanisms so you will need to make sure you have the correct terminal
removal tool for the job and know which side to approach the terminal locking
lit from press the release tool into the terminals locking latch and wriggle the
wire free out of the back of the connector at this points you can either remove
and replace the terminal with a new one or attempt to re tension the faulty
terminal again this process may differ depending on the design but having
correct tools is key .