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mattmag

join:2000-04-09
NW Illinois

1 recommendation

mattmag to westom

to westom

Re: [Help] Truck hit by lightning...

said by westom:



Very unusual to have such damage. Most surges pass through the truck body to earth without damage. For some reason, that current needed to pass through electronics to connect to earth. More often a struck vehicle does not suffer electronics damage.

I would have to strongly disagree with this. Every vehicle that I have ever encountered that was on the receiving end of a lightning strike has taken significant damage, and in most cases, not all of the problems are immediately detected.

The current absolutely *does not* have to pass through the electronics, as it is the strength of the magnetic energy field (EMF) associated with such a hit which is phenomenal, and is more than enough to thoroughly disrupt vehicle system electronics. This is also why the occupants of vehicle hit by lightning are relatively safe, since the body of the vehicle shunts the actual current around them. The effect of the EMF on humans is minimal, and, interestingly, has little effect on older cars before the days of multiple on-board electronic devices.

The most recent case I have experience with resulted in the vehicle ultimately being declared a total loss by the insurance company, as the initial "obvious" failures were followed by a series of other component failures, including internal shift modules, ABS motor failure, and two door control modules. Rarely will there be much visual evidence like "burned and melted wires" though, again, since it is EMF, not actual electrical current that caused the damage which makes advance diagnosis of a failure next to impossible.

My opinion without actually seeing the vehicle myself is that the hole in the earth is in fact where the strike departed the vehicle body, and if you examine the paint finish closely, you will find an area on the upper portion where the strike was taken as a deflection from the tree.

Basically, these cases are a real nightmare, and are rarely repaired completely the first try.
westom
join:2009-03-15

westom

Member

If EMF did that damage, then every nearby cell phone, wrist watch, and car radio was destroyed. Obviously not. Damage always means that current must pass through.

Lightning struck a building rod. That lightning rod was earthed by a wire only four feet from an IBM PC. So EMF created by 20,000 amps of nearby lightning also destroyed that IBM PC? Of course not. The PC did not even blink. EMF is a myth created when many do not understand how many 'insulators' are really electrical conductors.

Damage means a current was passing through that damaged device. He only sees vehicles with major damage. He does not see the so many others struck by lightning without damage.

Why are humans so safe in lightning struck cars? Same reason why electronics are only infrequently harmed by those strikes. Better auto designs means damage is less likely.

What specifically might be damaged? The list would be rather short. It starts by identifying the incoming and the outgoing to earth current paths. Then finding anything that was in that electrical path. What makes that challenging? Many have no idea that insulators (ie wood, linoleum, some plastics) are really electrical conductors.

workablob
join:2004-06-09
Houston, TX

workablob

Member

Do you mean EMI (Electro-Magnetic Interference)?

EMF (Electro-Motive Force) is just another name for voltage.

I think I get what you mean though.

Dave

mattmag

join:2000-04-09
NW Illinois

1 recommendation

mattmag to westom

to westom
said by westom:

Damage means a current was passing through that damaged device. He only sees vehicles with major damage. He does not see the so many others struck by lightning without damage.

I must say I am always enlightened by those here who pontificate their knowledge of all subjects, while those of us with many years of real-world experience in the automotive industry (over 30 actually) with hands-on experience as well are dismissed as not knowing of what we speak.

Good day.
nonymous (banned)
join:2003-09-08
Glendale, AZ

nonymous (banned) to westom

Member

to westom
said by westom:

What specifically might be damaged? The list would be rather short. It starts by identifying the incoming and the outgoing to earth current paths. Then finding anything that was in that electrical path. What makes that challenging? Many have no idea that insulators (ie wood, linoleum, some plastics) are really electrical conductors.

There may easily be more than one exit path and not all paths may be easily visible.
nonymous

nonymous (banned) to westom

Member

to westom
said by westom:

Why are humans so safe in lightning struck cars? Same reason why electronics are only infrequently harmed by those strikes. Better auto designs means damage is less likely.

I do not think they harden a vehicle against possible lightning strike. Now electronics in a vehicle are designed to withstand high temperatures under a hood of a car if placed there or just driving around in a bouncing vehicle all day. Plus designed not to cause accidents or break easily as lawsuits would happen. So by their very use and design are better off than some cheap product bought at a dollar store.

now airplane electronics and planes are tested for lightning strikes.
westom
join:2009-03-15

westom to nonymous

Member

to nonymous
said by nonymous:

There may easily be more than one exit path and not all paths may be easily visible.

Welcome to an art. Virtually no damage is visible - unless you are using test equipment that can see what eyes cannot. Many potentially destructive paths become obvious once simple concepts (ie insulators that are really conductors) are understood.

Problem of fixing surge damage is mostly about what the human does and does not know. But we know one thing. The destructive path(s) is from where lightning stikes to where it connects to earth. That never changes.

In one case, a mechanic kept replacing the computer - four times. Then we took over. Computer was never defective. He just followed the tech manual procedure four times rather than learn what those procedures were doing or asking. In that case, only three possibile defects existed: a control device, wire, and the computer. So he replaced the computer four times. That is what the diagnostics procedure told him to do. The actual problem was the control device.

It is a serious problem with all auto repair. To many only read directions rather than learn what directions are actually doing. Damage due to lightning is particularly challenging for many mechanics. Too many consumers then pay for replacing same components that were never defective.

Same solutions that harden a vehicle from lightning also harden those same electronics from other potential problems - such as an adjacent CB radio transmistter. Early auto computers, confused by nearby transmitters, were also easily succeptible to lightning damage. The solution for both are often same.

BTW, some of those solutions were pioneered in nuclear hardened weapon systems. Cars are routinely put into anechoic and equivalent test chambers for reliable operation during all types of electromagnetic interferenece. Better vehicles are struck by lighting without any damage. But again, welcome to an art.

Beezel
join:2008-12-15
Las Vegas, NV

Beezel

Member

said by westom:

said by nonymous:

There may easily be more than one exit path and not all paths may be easily visible.


In one case, a mechanic kept replacing the computer - four times. Then we took over. Computer was never defective. He just followed the tech manual procedure four times rather than learn what those procedures were doing or asking. In that case, only three possibile defects existed: a control device, wire, and the computer. So he replaced the computer four times. That is what the diagnostics procedure told him to do. The actual problem was the control device.

It is a serious problem with all auto repair. To many only read directions rather than learn what directions are actually doing. Damage due to lightning is particularly challenging for many mechanics. Too many consumers then pay for replacing same components that were never defective.

That's the difference between a true technician or mechanic if you will, and a parts changer. Mileage varies unfortunately.