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912 smoothing capacitor

  • jimdharris
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1 week 4 days ago #23017 by jimdharris
912 smoothing capacitor was created by jimdharris
I'm having electrical probs on my light aircraft and seeking possible causes. I find the smoothing capacitor (22000 mfd, 25 volts) is not a nice cylindrical shape (was it ever?) but is roughly hexagonal in cross section in the centre section tapering to circular at the ends. Surely would not have started life like that??? If it is dead what would the symptoms be?
If dead, is it a Rotax part or after-market?
Suggestions welcome!

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  • Bill Hertzel
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1 week 3 days ago - 1 week 3 days ago #23026 by Bill Hertzel
Replied by Bill Hertzel on topic 912 smoothing capacitor
The capacitor is an "Off The Shelf" Part. Nearly any 22,000uF, 25 volts cap will work.
They are readily available for under $5.

In the environment of an engine compartment. expect to replace it at least once every 10 years.
The Electrolyte eventually dries out over the years.
Capacitors are usually the reason that electronic devices eventually fail.

It should have been round with flat ends when new.
The failure mode is usually that it dries out, leaks Electrically, Gets Hot, Swells Up, and eventually blows its contents out the end cap making a mess.
It sounds like yours is about to blow!

The symptoms range from buzzing in the intercom, erratic voltage swings, Battery not charging to no symptoms at all depending on your specific wiring installation.

Bill Hertzel
Rotax 912is
North Ridgeville, OH, USA
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Last edit: 1 week 3 days ago by Bill Hertzel.
The following user(s) said Thank You: jimdharris

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