Prestolite (2 wire) Electronic Ignition Experiment

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Louie
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Prestolite (2 wire) Electronic Ignition Experiment

Post by Louie » Fri Feb 07, 2020 12:56 pm

I run the prestolite electronic ignition module in the mutt (2 wire). I have been reading a lot of those modules are failing as time goes on. One of my spares has suffered from all the potting compound leaking out all over the place.

I am a Electronics technician and want to disassemble one of these that has failed in the hopes of finding out why they fail. My curiosity stems whether they fail from moisture shorting out the electronics or simply dried up electrolytic capacitors or some other component failure. I want to find out if those of us that are using the prestolite ignition module are sitting on a ticking time bomb just waiting to leave us stranded somewhere.

If you have a burned out prestolite module or one that has all the potting leaked out I would like to obtain that from you. I will pay for your shipping expenses. In return I will post photos and technical information learned from the disassembly of the module here. I think this would be worth pursuing and we can all learn something from it.

And if anyone can ever locate a electronic schematic of the inside of the module, this would be very helpful. So far I have been unable to locate one.

Thanks in advance, Louie
Louie,
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GPW1263
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Re: Prestolite (2 wire) Electronic Ignition Experiment

Post by GPW1263 » Fri Feb 07, 2020 3:05 pm

Louie, I may have one but it will probably require my digging for it which is more a commitment of time, than effort.

The softening of the potting material can be a matter of heat build up and that, usually because someone left the master switch in the ON position. This has a similar effect on the potting material of the coil and, for the readers, if the coil gets fried to the point where it weeps down into the distributor, you can pretty much count on it coating the mechanicals of the spark advance mechanism, below. This must be checked out because there is the potential that it will seize up the mechanism after cooling.

The softening of the potting material on the electronic ignition module may also be the result of someone attempting to clean up the mess of a fried coil with solvents, typically sprayed in under pressure, without first removing the electronic ignition module. Solvents are quite capable of softening the potting material on the module. The one I propose to give you has been through this very process (and guess how I know... :cry: ). The potting material has become soft, like rubber cement. This particular module works only some of the time, until it gets hot. Ergo - I conclude that the potting material may also serve to keep heat away from the electronics.

Anyway, I'll see if I can locate it for you. No promises, tho..

Cheers,
TJ

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Louie
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Re: Prestolite (2 wire) Electronic Ignition Experiment

Post by Louie » Wed Feb 12, 2020 2:58 pm

Thanks TJ!
Louie,
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jnissen
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Re: Prestolite (2 wire) Electronic Ignition Experiment

Post by jnissen » Thu Feb 13, 2020 6:03 am

Agree that potting compound damage is likely from heat alone. If an improper impedance coil is used or a damaged coil then the semiconductor switch internally will overheat trying to pass the extra current. Over time this damages the device.

Believe you need at least 3.3Ohms in a 12V system and it differs if you have 6V or 24VDC systems.

Recently ran across odd cold weather issue with one of these. Was running a series ballast resistor and in our haste to wire and get it completed I ran the electronic device off the terminals of the coil. It resulted in less voltage going to the module. When cold it tended to have a low speed misfire.

Remeasured the coil and realized we didn’t need the ballast resistor. Now starts are near instant and spark is good and hot.


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