BATTERY CABLE [fried petronix]

[fordhealey]

upon replacing my battery cable, i found a small bare spot
where the cable had rubbed against the body.i'm guessing that is the reason that i fried a petronix ignition previously. it wasn't making constant contact, but i
believe the result of it grounding resulted in the meltdown (literally) of the module.it was well worth the expense of
replacing the cable. it saved the expense of replacing the new module, an solved the mystery of the meltdown.(not covered by the warrenty!!)
gregg

 

[AndrewMawson]

..mmm.. don't quite understand that. If the battery cable goes to chassis you'll get one heck of a current flowing round the cable / chassis loop which will not be nice but shouldn't affect the other electrics. I've not personally used a Pertronix but I assume it has a 12v feed, and uses a semiconductor to switch the coil to earth. I cannot imediately see how any of that would be affected by your intermittant shorting of the battery cable to chassis. /ubbthreads/images/graemlins/confused.gif

/ubbthreads/images/graemlins/england.gif

 

[Keoke]

/ubbthreads/images/graemlins/savewave.gif Gregg, :I agree: With Andrew. I think we need a bit of clarification here.-Keoke /ubbthreads/images/graemlins/laugh.gif

 

[fordhealey]

i run a 289 ford neg ground. could not a ground in the pos cable cause feedback from the alternator? i'm obviously not an electrical engineer.
gregg

 

[Keoke]

No gregg I don't think so.However, there is the unlikely , remote possibility that the intermitently shorting cable might generate a voltage trasient high enough to
damage the Pertronics module. I do know they are some what voltage sensitive but what the specific level is I do not know.On the other hand,It could have been just a coincidental random failure , it does occur sometimes.-FWIW---Keoke----- /ubbthreads/images/graemlins/patriot.gif

 

[fordhealey]

I burned up two modules using the petronix coil and a ballast resistor. i have a new alternator and solanoid.
if the cable wasn't causing the problem, i can't imagine
what else it could be. the alternator checks out fine.
i have a new optima battery. what else could be causing
a surge big enough to melt the module??all my grounds are good.
gregg

 

[Dave Russell]

gregg,
An unintentional ground of the main cable could cause heavy currents to flow in paths & directions that completely defy rational analysis of the situation. There could be dozens of unknown ground current paths involved. There could even be situations where there were momentary polarity reversals in certain circuits such as the ignition. Your analysis is as good as any.
D

 

[Keoke]

Gregg, I just don't know,there are several scenarios one could postulate but without test data to support would simly be speculation. However, here is a thought, check the magnet cam and make sure it does not rub on the mounting base plate in the distributor .Some years ago I looked into some Healey Pertronix module failures and determined it was due to additional heat generated when the Magnetic Cam rubbed on its mounting plate. Working with Pertronics the plate was reshaped to eliminate the interference which solved the problem and no further failures have been experienced. You might give Pertronics Eng People a call and see if it is a recognised problem with that kit or the installation,they are a good bunch up there.-FWIW---Keoke /ubbthreads/images/graemlins/driving.gif

 

[Dave Russell]

Keoke,
I'm under the impression that the problem that you describe was one of the early problems that led to the Pertronix original failure problems & consequently undeserved poor reliability reputation. But people have long memories when it comes to such things.

AFIK, the old defective units should have been off the shelves for several years now. I guess it is possible that there could still be a few "remainders" still kicking around. A good thing to check. I believe that the newer & correct cams are marked with the specific unit type number, which the older, questionable, units lacked.

Another obscure problem is that the magnet cam raises the rotor height slightly. Since replacement rotors can vary in height & the distributor cap terminal height can vary between caps, this extra height can cause rotor to cap contact if the wrong combination of parts happens to come together.

A couple of years ago, I tried to find a Pert. unit that would fit in my later model DM2P4 Lucas distributor. I finally settled on one that required the least modification. Just recently, I ordered another of the same model number. It is made completely differently (still same part number) & fits perfectly with no modification. Just to be sure, I ordered a spare, though I doubt if I will ever need it.
D

 

[Keoke]

Hi Dave, yes, it was during their early introduction to the British car market. To provide additional heat sinking, heat sink grease was added under the module. However, now the module is riveted to the adapter base plate. This later change was initiated because in some cases the module mounting studs were found to be chaffing the power leads inside the distributor-plus it is more economical to produce.Keoke--- /ubbthreads/images/graemlins/driving.gif

 

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[ThomP]

One of the major causes of Pertronix melt down is to simply leave the ignition switch on without the engine running. This might occur if you were listening to the radio while parked for instance. It might also occur if you were testing and tuning. I don't know if it's what caused your meltdown(s), but it is a common cause.

 

[fordhealey]

Remember!!this is a FORD engine. the first petronix(black)
module literally melted. we added the ballast resistor and
use the petronixII module. it died. went back to points. no
problems except with moisture. it's wet in key west a LOT.
went with a new petronixII and their coil and replaced the
battery cable. to this point(about 300 miles) no problems.
the engine runs stronger because the hotter spark seem to
burn the fuel a lot better. good at idle and at speed.if
this one goes,i'm wrong. but i still believe the cable was
causing the surge.
gregg

 

[fordhealey]

Re: BATTERY CABLE [fried petronix]THOMP

posted my reply before reading yours. you GOT it. I have
replaced all of my wiring with marine grade wire..including
the Ignition switch. It has NO accessory setting. only
on or off. the first module fried because i was working
on the motor with the switch and radio on and the engine not
running. the second one may have gone as a result of the same thing. i've since wired my radio hot so the switch does
not need to be on.i thought about that when the first module burned out, thought it my be running a steady current thru the module, but was told that wasn't the case.
apparently it is.
thank you
gregg

 

[ThomP]

Re: BATTERY CABLE [fried petronix]THOMP

I'm under the impression that the Pertronix Ignitor II does not have this problem. I don't know this for certain, but I have heard through the grape vine, that they have a microprocessor looking at the pick up and if it is not "opening" and "closing", it simply turns off. A simple current check with the Ignition switch "on" will confirm or deny this rumor and you'll know if you're safe or not.

An automotive system is FULL of spikes; every time you turn the starter off, fire the ignition or dis-engage the overdrive, the excess energy is dumped back into he electrical system so fast the battery cannot adsorb it. You can literally observe voltages of 100s of volts in an automotive system, thankfully these voltages only last a few millionths or thousandths of a second, but they are long enough to affect semiconducorts. Experienced designers provide protection for their electronic stuff in an automotive environment (I think Pretronix is experienced) and this is not an issue, however, from time to time, "the mother of all surges" comes along and destroys those semiconductors, including the protection circuitry.

 

[AndrewMawson]

Re: BATTERY CABLE [fried petronix]THOMP

[ QUOTE ]
An automotive system is FULL of spikes; every time you turn the starter off, fire the ignition or dis-engage the overdrive, the excess energy is dumped back into he electrical system so fast the battery cannot adsorb it. You can literally observe voltages of 100s of volts in an automotive system, thankfully these voltages only last a few millionths or thousandths of a second, but they are long enough to affect semiconducorts. Experienced designers provide protection for their electronic stuff in an automotive environment (I think Pretronix is experienced) and this is not an issue, however, from time to time, "the mother of all surges" comes along and destroys those semiconductors, including the protection circuitry.

[/ QUOTE ]

But as I understand it the two modules 'melted' so presumeably they overheated bigtime - much more likely to be that the engine was left with the ignition on but not running. If the coil draws perhaps 4 amps (typical of a sports coil) and the semiconductor has a forwards pass voltage of maybe 400mV then it's only 4 x 0.4 = 1.6 watts being disipated which doesn't seem much. And if you consider it's expected in normal conditions to be turning on and off at maybe a 50% duty ratio, 'normal disipation' would be 1.6 x 0.5 = 800mWatt. Not a big margin - surely the design anticipated the higher disipation /ubbthreads/images/graemlins/confused.gif

 

[Healey 100]

Re: BATTERY CABLE [fried petronix]THOMP

This thread has reinforced my belief that conversion to electronic ignition systems in these Healeys is not always the best idea.

I know the Pertronix unit has an excellent reputation and many advocates out there. But each car and installation has electrical and thermal quirks that cannot always be handled well with a universal aftermarket electronic system.

I have many old cars with electrical points. Of the myriad of problems I have had with these cars, the points are probably the least troublesome and most repairable of any parts in the car. I don't understand the need to convert to electronic ignition, any more than I need to convert to fuel injection. Yes, they both work well when properly engineered. But retrofitting is not without its risks.

See you on (or the side of) the road!

Bill.