chrome ignition box: high voltage at the outside?

[360duster]

Hi Guys, today i got an strong electrical shock when i touched the device in the middle of the heat sink of the chrome box supplied by FBO (is it a transistor?). Is this normal or is it a sign of my box going south??? Anyone experienced the same? There´s no voltage at the outside housing and the heat sink itself, only at the electronic device. Thanks for Info!

Michael

 

[66plyValiant]

Hi Guys, today i got an strong electrical shock when i touched the device in the middle of the heat sink of the chrome box supplied by FBO (is it a transistor?). Is this normal or is it a sign of my box going south??? Anyone experienced the same? There´s no voltage at the outside housing and the heat sink itself, only at the electronic device. Thanks for Info!

Michael

should be no voltage high enough to shock you one the ECU, all it does is see distributor signal and turns the low voltage side of the coil on and off at the very most there is 14 volts at the ECU and normally much less

any chance you bumped a spark plug wire while you were in there?

 

[67Dart273]

There most certainly IS high voltage on the heat sink / transistor. I used to have trouble with this in my old FJ-40 Landcruiser when I had the (various) 360 / 340 / 318 engines in it. I'd get out in the mud and snow, and get the ECU wet, and the thing would miss and argue and generally piss me off

This is the coil negative, and this pulse can be well over a hundred volts and more. If you look at this on a scope, it will be very similar to a break points ignition waveform

This is because of what is known as "inductive kick" from the inductance of the coil. You can EVEN get shocked (lightly) of an inductor or coil with an ohmeter. Take a coil, and set your ohmeter to low ohms. Hold the probes so that your fingers are contacting both. Touch and then disconnect the probes from the coil, try it both between the two coil primary (stud) terminals, and between the coil neg. and coil "tower."

 

[BillGrissom]

Ditto above. When you switch off any coil (primary or secondary side), you get a high-voltage kick that either jumps a gap (spark plug), gets dissipated in a diode (often integral with the switching transistor) or bounces back & forth in the capacitance of the wiring. Most switching transistors I have used (MOSFET or IGBT) have clamping voltages between 30 and 1000 V. Automotive ones are usually on the low side. I remember a story of a preacher outside Atlanta who caused a fuss because he shocked kids sitting on his "stool of truth" when they answered bible questions wrong. He claimed it was just a tickle because he used a 6 V lantern battery. He didn't mention the big coil in the circuit.

 

[360duster]

ok guys, i got it. Maybe Don from FBO can say sth., i asked in another Thread. I´ll leave it as it is at the moment, it seems not to be a problem.

Thanks so far!

Michael

 

[KitCarlson]

And the coil negative terminal will have high peak voltage too during spark. Typically the heatsink has a coil driver transistor that is insulated from the heatsink. The transistor collector or drain has a connection to the coil negative terminal. Careful inspection may show the typical TO-3 package on top of heatsink with a plate, and what looks like fiberglass cloth, or mica sandwiched between.

As a side note:
Modern coil driver semiconductors have a built-in clamp voltage called avalanche protection. While the protection works well in the short term, long term damage may occur from running with a pulled spark plug cable. Normal spark action clamps the voltage, with the open spark cable, the avalanche protection comes into play, and the repetition builds heat and damages the driver.

 

[rumblefish360]

He he he he, felt like someone room a mean *** hammer to your arm huh?!!!!!
That DC is a real *** kicker.

 

[KitCarlson]

Not DC, it is a short pulse, about 100 uS in duration, for each spark. The peak voltage is about 400V. 400V DC is much worse, I know from experience. I developed a CDI at an early age, and made a few mistakes. It can leave white burn marks on the skin.

 

[67Dart273]

long term damage may occur from running with a pulled spark plug cable. Normal spark action clamps the voltage, with the open spark cable,

THIS is an EXTREMELY important point with any/ all modern electronic ignitions

To put this into "earthly words," LOL, here is what happens

Guys sometimes talk of "pulling plug wires" to see if a cylinder is dead

NEVER do that. Instead, ALWAYS GROUND that position. I usually either put small brads down beside the wires in the cap, or use a grounded probe at the cap while pulling a wire out with fuse pullers. Loosen the wires before hand

Spark voltage is just like lightning. It is seeking the "shortest path to ground." In and operating engine, this "shortest path" is always through the relatively small plug gap, which is EFFECTIVELY smaller (lower resistance) because of conditions inside the cylinder

This is what Dave means, above, when he says

"Normal spark action clamps the voltage"

The normally hooked up cap, rotor, wires, and plugs (going to ground) LOWER (load) the coil voltage to the normal "firing" voltage of the plugs

When you pull a plug wire, the coil voltage now suddenly has no place to go, the coil voltage goes to peak open voltage.

THIS very very high, abnormal voltage "reflects" this pulse backwards through the coil, and a high voltage pulse now appears "back" in the primary ---in the electronics switching

This can cause very bad and terminal failures to electronic ignitions, and INCLUDING the coil itself.

 

[KitCarlson]

Some damage is the result of carbon tracking on an undesired spark path, and is nearly invisible. Other damage may occur in the insulation of the coil windings. Damages are not easy to test for, but degrade the ignition capacity, for adverse conditions.

When I saw the TrailBeast HEI demo video, my reaction was oh my.

 

[TrailBeast]

Some damage is the result of carbon tracking on an undesired spark path, and is nearly invisible. Other damage may occur in the insulation of the coil windings. Damages are not easy to test for, but degrade the ignition capacity, for adverse conditions.

When I saw the TrailBeast HEI demo video, my reaction was oh my.

And yet I have not in my entire life had an ignition system fail from letting the spark jump.
By luck, or by chance I'll still take it.
I get that you are saying that there is a possibility of partial degredation.
I figure, if the spark will jump a couple of inches without jumping internally it's easily capable of running on an engine.

 

[KitCarlson]

And yet I have not in my entire life had an ignition system fail from letting the spark jump.
By luck, or by chance I'll still take it.
I get that you are saying that there is a possibility of partial degredation.
I figure, if the spark will jump a couple of inches without jumping internally it's easily capable of running on an engine.

I speak from experience, from actual laboratory tests of high voltage equipment, stressed beyond limits, to eventual failure. After failure, components are dissected, and failure modes determined.

While volts per distance vary with air pressure and other environmental factors, a 2" (about 51 mm) gap requires about 150,000 volts to initiate a spark. I will let it go at that.

 

[TrailBeast]

I speak from experience, from actual laboratory tests of high voltage equipment, stressed beyond limits, to eventual failure. After failure, components are dissected, and failure modes determined.

While volts per distance vary with air pressure and other environmental factors, a 2" (about 51 mm) gap requires about 150,000 volts to initiate a spark. I will let it go at that.

Now see, you are doing precise scientific work and I'm just making a vinigar and baking soda volcano that works.

 

[RustyRatRod]

"Blah blah blah I speak from experience, I have a lab I test high voltage equipment dissect and determine stuff" Oh good grief. You need some humor. You been in the lab too long. lol

[ame="http://www.youtube.com/watch?v=2fjcJp_Nwvk"]Rockwell Turbo Encabulator Version 2 - YouTube[/ame]

 

[itate]

Apparently a shock from the control unit is normal, from the 1973 Chrysler Electronic Ignition Diagnosis booklet.

 

[BillGrissom]

I figure, if the spark will jump a couple of inches without jumping internally it's easily capable of running on an engine.

I used an IGBT transistor switch at my last company to drive an air coil for an electromagnetic detector (similar to a metal detector). To test the circuit, I had it pulsing an old Mopar coil, with the spark jumping 2" in open air. When it hadn't failed all weekend, I decided it would work fine (it did). However, it is easy to spark at 1 atm pressure, and even easier in a vacuum where sparks readily jump many meters. In an automotive engine, the spark must work at 200 psi cylinder pressure, which is much harder and why a 0.060" gap is about the limit for most ignitions.

 

[360duster]

Haaa, that´s funny! So they found that out in the 70´s....

Thanks at all for the support!

Michael

Apparently a shock from the control unit is normal, from the 1973 Chrysler Electronic Ignition Diagnosis booklet.

 

[KitCarlson]

"Blah blah blah I speak from experience, I have a lab I test high voltage equipment dissect and determine stuff" Oh good grief. You need some humor. You been in the lab too long. lol

That is complete truth, in a tender way, I am likely crazy, from 50 years of work related (shock) injuries. I am a hands on EE, that has developed many products and devices. My career was non stop, now retired, still doing power electronics work. My problem is I cannot stop.

 

[TrailBeast]

That is complete truth, in a tender way, I am likely crazy, from 50 years of work related (shock) injuries. I am a hands on EE, that has developed many products and devices. My career was non stop, now retired, still doing power electronics work. My problem is I cannot stop.

Uh oh.
Kit is going to get sucked into one of his projects and scattered into the atmosphere as random electrons, and then come back through our computers like one of those faces you see on a screen in a sci fi movie.

 

[TrailBeast]

However, it is easy to spark at 1 atm pressure, and even easier in a vacuum where sparks readily jump many meters. In an automotive engine, the spark must work at 200 psi cylinder pressure, which is much harder and why a 0.060" gap is about the limit for most ignitions.

Learned that in shop class about 1971 using and old air pressurized spark plug cleaner/tester.

 

[KitCarlson]

I am hoping to pass, from lightning.

I had a close call with ball lightning when building my shop/lab. It was a rare act of nature, on a clear sunny day. I was at a faucet cleaning concrete tools, when I felt a strong electric field raise the hair on my neck. Two seconds later about 75' away, to my right, a gold ball about 8" in diameter, disappeared as it exploded, leaving a 10' diameter clear area in the tall grass, and grass confetti in the air. My building is a galvanized steel arch building 16' H, 40'W, 60'L, why it exploded 2' off the flat ground nearby, and not on the well grounded building is a mystery. No, I did not have gas that day, gas service, or electrical service on the property. What I experienced, does not fit well with my understanding of electromagnetic field theory.

 

[TrailBeast]

I am hoping to pass, from lightning.

I had a close call with ball lightning when building my shop/lab. It was a rare act of nature, on a clear sunny day. I was at a faucet cleaning concrete tools, when I felt a strong electric field raise the hair on my neck. Two seconds later about 75' away, to my right, a gold ball about 8" in diameter, disappeared as it exploded, leaving a 10' diameter clear area in the tall grass, and grass confetti in the air. My building is a galvanized steel arch building 16' H, 40'W, 60'L, why it exploded 2' off the flat ground nearby, and not on the well grounded building is a mystery. No, I did not have gas that day, gas service, or electrical service on the property. What I experienced, does not fit well with my understanding of electromagnetic field theory.

When I was a kid up in the Sierra Nevada mountains we had one come through the livingroom picture window and float all the way across the livingroom and down the hallway before it just disappeared.
That was one of weirdest things I think I have ever seen, and the same as yours (No idea why it would follow that path instead of jumping to plumbing or our grounded stone fireplace)
It was bright blue with an orange halo around it.

I remember jumping up to follow it, but my Mom said to stay where I was.
I was about 8 feet from it at the closest point as it went through the room.

 

[mopar head]

I am hoping to pass, from lightning.

I had a close call with ball lightning when building my shop/lab. It was a rare act of nature, on a clear sunny day. I was at a faucet cleaning concrete tools, when I felt a strong electric field raise the hair on my neck. Two seconds later about 75' away, to my right, a gold ball about 8" in diameter, disappeared as it exploded, leaving a 10' diameter clear area in the tall grass, and grass confetti in the air. My building is a galvanized steel arch building 16' H, 40'W, 60'L, why it exploded 2' off the flat ground nearby, and not on the well grounded building is a mystery. No, I did not have gas that day, gas service, or electrical service on the property. What I experienced, does not fit well with my understanding of electromagnetic field theory.

This is funny, My Ex told a story of when she was a kid, a friend and her were walking down a road, at night, then were being chased by a ball of fire! I thought this was pure BS until in the last few decades I`ve seen on tv about ball lightning. That is what they were probably experiencing.:wack:

 

[KitCarlson]

I remember jumping up to follow it, but my Mom said to stay where I was.
I was about 8 feet from it at the closest point as it went through the room.

Smart Mom, the sound of the one near me reminded me of a small balloon my Dad once filled with oxygen and acetylene, placed in a paper bag and lit. It would have broken all the windows in the house.

 

[TrailBeast]

Smart Mom, the sound of the one near me reminded me of a small balloon my Dad once filled with oxygen and acetylene, placed in a paper bag and lit. It would have broken all the windows in the house.

Oh, I love oxygen/acetylene ballons
Been playing with that stuff for years.

When I lived in Cal my brother and I filled a 55 gallon plastic trash bag with it, and another bag of helium and taped them together.
Then I taped about 12 feet of cannon fuse to the gas bag, lit it and let er go.
HOLY HELL Batman.

I never knew that town had that many cops and firetrucks in it.
They were everywhere for about two hours.
I had a friend call from 13 blocks down town and said his dishes were all rattling in the cupboards.

When it went off you could see a huge concusion wave in the air spreading out from the ignition point.

That stuff can be really dangerous, especially in an inclosed area.