Radio Noise Capacitor - Chevelle Tech
Electrical & Wiring Troubleshooting electrical problems.

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post #1 of 7 (permalink) Old Feb 1st, 19, 11:16 AM Thread Starter
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Lou
 
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Radio Noise Capacitor

Hi,

would anyone happen to know if Radio Noise Capacitors go bad. I've got an original that was bracketed to my coil. It still looks good on the outside but am not sure what's going on the inside and what if anything goes bad inside. It's that silver cylinder about 5/8" in diameter and about an inch and half long with one wire coming out.

Thanks

Lou
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post #2 of 7 (permalink) Old Feb 1st, 19, 11:37 AM
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Re: Radio Noise Capacitor

You can check it with an ohmmeter

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post #3 of 7 (permalink) Old Feb 1st, 19, 11:51 AM
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Re: Radio Noise Capacitor

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Originally Posted by 1943MB View Post
Hi,

would anyone happen to know if Radio Noise Capacitors go bad. I've got an original that was bracketed to my coil. It still looks good on the outside but am not sure what's going on the inside and what if anything goes bad inside. It's that silver cylinder about 5/8" in diameter and about an inch and half long with one wire coming out.

Thanks

Lou
All components can go bad. If it shorted it would kill the engine and if it is open you will just have more radio ignition noise coming out of the speakers. Easy to check with a meter, especially an older analog meter or a modern DVM. Just connect the leads between the wire to positive lead and the black lead to the case and you will see the resistance change as the capacitor charges which is how it should be. It will go from a short to open while it charges if your meter has the ability. I am not running one on my Chevelle but I am also no longer running points and I have been told its not needed by wiring/electronics specialist with electronic ignition. However it will not hurt leaving it on if its not shorted.
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post #4 of 7 (permalink) Old Feb 1st, 19, 12:14 PM Thread Starter
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Re: Radio Noise Capacitor

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Originally Posted by Billdini View Post
All components can go bad. If it shorted it would kill the engine and if it is open you will just have more radio ignition noise coming out of the speakers. Easy to check with a meter, especially an older analog meter or a modern DVM. Just connect the leads between the wire to positive lead and the black lead to the case and you will see the resistance change as the capacitor charges which is how it should be. It will go from a short to open while it charges if your meter has the ability. I am not running one on my Chevelle but I am also no longer running points and I have been told its not needed by wiring/electronics specialist with electronic ignition. However it will not hurt leaving it on if its not shorted.

Hi thanks for the info. I've got one black wire from the capacitor. Is that a red connect or a black connect from the meter. Where does the other wire go ? What setting is the meter set to. What am I looking for on the meter. Meters need batteries which go bad. I don't much care for meters for what that's worth. Can I check it with a 12 volt light probe and a 12 volt battery ?

Thanks
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post #5 of 7 (permalink) Old Feb 1st, 19, 12:48 PM
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Re: Radio Noise Capacitor

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Hi thanks for the info. I've got one black wire from the capacitor. Is that a red connect or a black connect from the meter. Where does the other wire go ? What setting is the meter set to. What am I looking for on the meter. Meters need batteries which go bad. I don't much care for meters for what that's worth. Can I check it with a 12 volt light probe and a 12 volt battery ?

Thanks
I don't believe those caps are polarized meaning they are not polarity sensitive but to be safe connect your red OHM meter lead to the wire coming out of the cap and the black wire to the cap case. Use a lower OHM setting. Remember you are testing resistance and not voltage. Also make sure the wire is disconnected from the coil or it could back feed through the points. Nope test light will not help. You might also want to test the cap case to engine ground to make sure all your ground connections are good. As far as meters needing batteries that is a must since resistance applies a battery voltage to the component being tested. Ground the wire coming out of the capacitor for a couple seconds to make sure it isn't holding a charge before you check for resistance.
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post #6 of 7 (permalink) Old Feb 1st, 19, 1:32 PM
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Re: Radio Noise Capacitor

You put one lead on the case and the other on the wire lead and then reverse the meter leads.
That charges and discharges the capacitor and the meter will go up, then back down as it charges then discharges.
You can do it over and over.
If the meter does nothing OR stays up, the capacitor is bad.

A larger capacitor (which it's case is not connected) but the theory is the same.
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Last edited by Dean; Feb 2nd, 19 at 10:50 AM. Reason: Left an "n" out
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post #7 of 7 (permalink) Old Feb 2nd, 19, 10:42 AM Thread Starter
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Re: Radio Noise Capacitor

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Originally Posted by Dean View Post
You put one lead on the case and the other on the wire lead and then reverse the meter leads.
That charges and discharges the capacitor and the meter will go up, then back down as it charges the discharges.
You can do it over and over.
If the meter does nothing OR stays up, the capacitor is bad.

A larger capacitor (which it's case is not connected) but the theory is the same.
Start Run Capacitor Testing Using A Cheap Meter DIY (HVAC/Stereo/Microwave/Electronics) Service - YouTube

Okay, got it. Thanks
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