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Can bad cdi fry the ac ignition power coil?

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danmace

New member
hello, what can damage the ac coil under flywheel that coil what charge capacitor inside cdi, friend want to try his cdi from the same engine, and after connecting his cdi, something damage coil under flywheel, before i check with multimeter and dva and coil output about 300V right now 0v i check with resistance and coil reads as open, so i think something broke or fry wire inside coil.i want know what mistake i did so i dont repeat it in future
 
So test that coil with your meter.-----No need to remove the flywheel to do the testing.-----Note----It is indeed called a " charge coil "
 
i tested it and like i wrote in 1 post, it output 0v and i check resistance and it not have any resistance, so coil must fry, but question is why?
 
haha im not angry at him, im just curious what can damage coil, possible is when you crank and its nothing attached to coil then voltage cumulate inside coil and then burn winding?
 
i see it but somehow coil is dead, output 0v and reads infinite ohms, and i check one wire going from coil and wire is fine
 
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danmace said:
haha im not angry at him, im just curious what can damage coil, possible is when you crank and its nothing attached to coil then voltage cumulate inside coil and then burn winding?
Click to expand...

If it is not connected to anything, there is no current flow (Watts), so no heat to burn anything. If only one lead is connected, I suppose voltage could arc to ground across damaged windings. That's speculation.

"Charge coil" charges the CDI capacitor. The other coils are alternator coils to charge the battery.
 
danmace said:
i tested it and like i wrote in 1 post, it output 0v and i check resistance and it not have any resistance, so coil must fry, but question is why?
Click to expand...

In time, stator coils fail even when everything is in tip top running condition... failing simply due to the heat generated by the magnetic friction that exists by those flywheel magnets flying by. Usually it results in a cracked stator with a sticky looking substance dripping down on the powerhead area... but the failure can also be simply a shorted or broken wire within that sealed unit as you describe.

A stator failure can also result from a damaged rectifier. If the rectifier cannot convert the AC voltage from the stator to DC voltage to charge the battery, the voltage backs up at the stator, and it will definitely overheat. When this happens, for some reason, it is the coils that supply AC voltage to the powerpack capacitor that seems to fail first.

And finally.... if anyone works on the engine who has no idea how the ignition system works... and applies 12v to that stator... yeah that'll fry it rather quickly.

Now.... If you're asking if a faulty powerpack will cause damage to a stator, the answer is no... not unless you have it wired wrong that might result in one of the above scenarios.
 
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ok, so charge coil cant be damaged if there is no load (nothing connected to coil wire) just want to know so in future i dont blow coil again.
 
I have a bad coil, and I'm replacing it. Someone told me that if my CDI was terrible, it could ruin my new lock. Unfortunately, I don't have the peak reading adapter for my multimeter to test my CDI to check before putting on the new coil. I know the CDI accepts the charge from the stator, holds it and at the appropriate time releases it to the ring where it is intensified and sent socool to the plug to provide the spark for combustion. I don't see how the CDI could ruin the coil, but my knowledge of this electrical stuff is minimal, so I figured I'd ask better-informed ones.
 
It depends on every situation in particular. The CDI is not easy to diagnose because the observable symptoms of a faulty CDI box can lead to different directions. Sometimes, a bad CDI does not cause sparks at all. Again, when a CDI box is about to go wrong, it can lead to misfires, issues with starting, rough running, or even stall the motor. My suggestion to you would be to call a team of workmen to see and fix your issue. I know only this website https://www.marvellous.sg/aircon-chemical-wash/. I think my post will make light for you, and I wish you luck repairing your Ac!
 
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