Nothings Shocking Now: An Electrical Primer (Part 2)

This week, part 2 of the MW electrical primer series comes with real- life electrical frustrations from 4 different clients cars as well as electrical challenges of my own.  One clients repair was a simple fix with just an easy to find broken wire.   Another may have totalled the vehicle from a dash fire which resulted from a parking lot mishap and power mirror wiring damage. The third failure got a mother and children stranded in the middle of nowhere because simple, basic maintenance had not occurred on the battery connections.  As for the 4th problem child, it is still under investigation for very strange but isolated behavior in the power window circuit.  

Reliable electrical power generation, storage, and distribution in cars is fully necessary these days, but one small issue can lead to a range of failure modes resulting in all manner of results from minor frustrations to catastrophic large-scale system meltdowns, fires, and eye-poppingly painful repair bills or replacement costs. 

 
There is always an underlying concern with automobile or other transportation machinery electrical systems because of the intense environment that the wiring and componentry must endure as a matter of course for the job to be done.  Intense heat and cold with rapid temperature changes, vibration and road bumps as well as too many opportunities for physical damage to wiring or devices make vehicular electrical systems subject to much more potential for damage, failures, short or open- circuits, and even electrical fires than most other types of electrical systems.

Electrical issues can be as simple as a broken wire or battery corrosion (another article will cover this one later), to as complex and disastrous as is physically possible in this universe.  Electrical issues run as wide a gamut of failure and manifestation of problems as can be found in any system and can spread through other, seemingly unrelated systems, making the determination of initial cause a painful lesson in electrical investigation. 
 
Most rookie mechanics, and even many old- timers, are so intimidated by electrical issues that they will not even touch them.  I cannot blame them one smidge.  I have literally given myself headaches studying electrical diagrams and schematics trying to understand where a fault could be to cause the issues I am seeing and the data I am reading on my test equipment.  Its no joke.  Electrical is very frustrating because so many problems behave similarly, and just because you know what the fault is, finding where that problem lies can be a whole other nightmare by itself.

Wires in cars can be tens of feet long and can have damage anywhere along their length without anything wrong being obvious from the outside.  There are dozens of individual components that can fail or partially fail, mimicking other problems in other components.  A switch or relay can stop working in one or more ways;  overheating and melting of wires can occur in many different places without easy to recognize damage;  snow and ice can accumulate and rip wiring down from underneath;  rocks or other road debris can be thrown violently up at the undercarriage and damage wire looms or crush electrical channels; etc, etc, etc...  Cars live a dangerous life, the electrical system even more so.

Wiring in most machines is done in terms of a 'harness' or large bundle of pre- measured and pre- taped wires, for each of many various sub-systems, all of which connect to each other by big multi-wire plugs that tie all of these systems together into one coherent (we hope) power distribution network.  From the front of the vehicle to the rear, covering engine and drivetrain control systems, all the various lights, heating and cooling systems, audio, control and comfort systems scattered everywhere, safety and notification sensors and indicators of all types...  Then add in all the possible user- added modifications that may or may not be causing problems and we have a mystery whose layers can be manifold, sundry and highly complex to say the least.  A problem in one circuit can quickly spread to neighboring wires and cause unrelated problems elsewhere.  The glitchy switch that you bring your car to the mechanic to have repaired could be the result of another problem going on somewhere entirely separate and in a system fully unrelated except for the fact that the wires run side by side inside a harness.

Finding a fault inside a wiring harness that may be 15 or more feet long and contain 40 or more wires can be very time consuming and labor and mental energy intensive.   Tracking that fault back to initial causality then determining the best course of action for repair can prove fatal for more than a few brain cells.  The labor intensive nature of electrical diagnosis can be intimidating when the invoices can go into the hundreds of dollars just to find out what is wrong, then many hundreds, even thousands more, to actually perform the repairs.  After these expensive repairs, there is no saying some other unrelated parts weren't damaged and will fail sooner than later and could cause a whole new round of irritation and costs.

Back when I was a teenager in the  mid 1980s, my dad bought himself a Lincoln- a nice one too.  What a beautiful car.  I will write a more in- depth article on this car and the scenario I speak of here at some point, but for now, its enough to know that a $5 sensor under the hood caused the exhaust system to overheat and melt a massive bundle of wires together, shorting out many electrical circuits and causing months of headaches for my dad to rewire and make useable again.  When  the car got sold a few years later, it was with full disclosure of some issues still lingering in there, and possible future frustrations that may re- arise. 

In the case of my dads Lincoln, its possible dad may have had time to change out the sensor before the overheat could happen, but its hard to say if there was enough warning.  Its tough to know how long the problem had been going on, or if it was simply a sudden failure in that sensor that lead to the exhaust overheating.  Final causality was found, but preventability is impossible to know. 

In some cases its neglect that causes the problems, some its stupidity or worse, ignorance.  In most cases though, I find that electrical issues should be filed under the 'SHIT HAPPENS' category.  Unless directly related idiocy was found, its best to chock it up to fate or whatever gods govern machines and electrical sillyness you want to blame.  High value systems that do so much and make so much possible can suffer high value damage and have high cost repairs.  Its part of reality now if you own a modern machine.  We gotta get used to it, but we don't have to like it.  I offer my condolences.  

This series on electrical systems will continue with a few more articles containing explanations and exercises to help with understanding,  so check back for the next installment. 

Heres to your machines longevity, MW out...