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HelicopterGasser Model RC HelicoptersEngines › ignition coils output voltage
05-15-2015 02:34 AM  25 months agoPost 1
flyinfriend

Senior Heliman

North American continent

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I am trying to confirm the functioning of the coils as I am not getting any spark. Does anyone know what the out put from the spark plug cable to engine ground should be?

The resistance on both coils is close to spec in the Zenoah manual so that isn't telling me which coil may be bad.

I'd rather not pay $85 for both red and grey coils if I can figure out which one is bad.

Any suggestions would be appreciated.

Thank you,

Tom

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05-15-2015 02:57 AM  25 months agoPost 2
RM3

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Killeen, Texas - USA

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unfortunately you will not be able to read the voltage from the primary nor the secondary coils with a typical voltmeter.

the voltage produced by the primary coil is a short AC waveform that is too fast to be sampled by majority of electricians voltmeters.

the output of the secondary is a minimum of 10,000 volts and will likely zap your voltmeter.

sadly the only way to check is by swapping them out... unless you have a specialized high voltage probe for an oscilloscope or a high voltage insulation tester there is no other way.

showing a preference will only get you into trouble, 90% of everything is crap...

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05-15-2015 03:13 AM  25 months agoPost 3
flyinfriend

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North American continent

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Thanks for the info RM3. I was trying to read the voltage off of the spark cap and the engine ground. I was barely getting a milli volt reading from it while pulling the starter. If I put the meter to the 20 volt setting to read I saw no voltage output reading at all however reading the resistance of the two coils various outputs matched fairly closely with Zenoah's specs.

Evidently reading the resistance isn't an indicator of a good coil. The last time I had a coil go bad the ohm measurements matched the manual as well but replacing one of them fixed the issue.

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05-15-2015 03:50 AM  25 months agoPost 4
RM3

Elite Veteran

Killeen, Texas - USA

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you can however check the Capacitor with a regular voltmeter...

Set your voltmeter to read resistance, as high as it can go... (unless its autoranging). disconnect the cap from everything (very important). Read the resistance across the cap... the resistance should quickly go to infinite (open circuit) as the capacitor basically charges up from the tiny amount of current from the voltmeter... if you do happen to read a resistance across the capacitor, then its bad (leaky). dont use your fingers to hold the probe tips against the capacitor connections or the voltmeter will read the mega ohm resistance across your body.

its not often that the coils go bad (unless the ignition has been run with no plug too much causing the high voltage to short in the secondary over time)... but the caps do tend to die with age and short out internally to some extent and in effect short the current spike from the primary before it can be inductively multiplied by the secondary.

showing a preference will only get you into trouble, 90% of everything is crap...

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11-22-2016 07:21 PM  7 months agoPost 5
Rojoalfa

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Punta de Mata, Monagas-Venezuela

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/
/

I decide to open a faulty Zenoah coil red.
I was considered to find just coils... That was not the case.

I found a CDI inside...

Black wire is just a kill switch.
Red wire is the output to the ignition coil to spark plug.

At this time, I am not sure what is the faulty component.

Now, with my dremel carefully, I will find out...

/

Saludos cordiales,

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11-22-2016 07:41 PM  7 months agoPost 6
Rojoalfa

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Punta de Mata, Monagas-Venezuela

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/
/

Capacitor Is below circuit board...I think...

/

Saludos cordiales,

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11-22-2016 07:53 PM  7 months agoPost 7
RM3

Elite Veteran

Killeen, Texas - USA

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its not a CDI circuit depicted.... looks like a wave shaping bridge circuit as its using a SCR to effectively short out 1/2 of the voltage ac wave from L1... then transfers the remaining "spike" via C1... just my hypothesis...

showing a preference will only get you into trouble, 90% of everything is crap...

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11-24-2016 02:44 PM  7 months agoPost 8
Rojoalfa

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Punta de Mata, Monagas-Venezuela

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/
/

Well, my point is checking red and black cables Is doing nothing.

If capacitor is out, red cable has no connection.
If coil is out, there is no way To know that.

/

Saludos cordiales,

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11-26-2016 06:08 PM  7 months agoPost 9
Rojoalfa

Senior Heliman

Punta de Mata, Monagas-Venezuela

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/
/

Faulty capacitor LG 334K ( 650V?)

/

Saludos cordiales,

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