rotax 912 Capacitor

19 posts in this topic

Posted (edited)

Do any of you have a install picture of the 22,000 mfd capacitor for the Rotax 912?

Edited by lv2plyguitar

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Posted

What are you wanting to see?

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Posted

I want to understand the wiring.  I have the diagram but want others interpretation to make sure I am right. 

Thanks

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Posted

Okay.  No offense intended.

I wired mine just as the diagram shows.  Only, at the time I didn't know that a Capacitor is polarized.  The first one exploded in rather spectacular fashion when I powered up the main buss...

 

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Posted

Okay so one wire to ground and 1 to c correct?  

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Posted

Yes.  The Capacitor will have a definite mark on one of the terminals or on the body side of one of the terminals.  This is the GROUND side.

Note the stripe or indicator on the photo below.  These all denote the negative (ground) terminal of the capacitor.  

neg_cap_marking.jpg

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Posted

One wire to ground the other wire goes to "C" terminal from the regulator, which is also connected to the "R" and "B+" terminals.  All three of these will be connected together.

See figure 74-12, page 16, Chapter 74 of the Heavy Maintenance Manual.

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Posted

Okay.  No offense intended.

I wired mine just as the diagram shows.  Only, at the time I didn't know that a Capacitor is polarized.  The first one exploded in rather spectacular fashion when I powered up the main buss...

 

so I'm not the only one...

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Posted

...followed by the secondary explosion in my shorts when I realized my Dynon FMS/EMS was on the same circuit.  Luckily no damage.

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Posted

One other word of caution install the capacitor with the terminals up.  They are vented and the vent can become plugged if not properly installed and cause them to explode.

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Posted

Here is a install picture.  Do you guys agree with it?

Image result for rotax 912 capacitor wiring

 

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Posted (edited)

Yes.  Then, also coming off the (+) terminal of the capacitor is the line to the main buss and battery (the second white wire from the left?).

(triple check the polarity of the capacitor)

Edited by Av8r3400

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Posted

What I don't see is a dedicated ground to the case of the regulator perhaps it is on the firewall side of the mounting bolt.

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Posted

Good catch, Paul.  Hooking the case of the regulator to a dedicated ground buss would be a good idea.

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Posted

Sorry I am not an electrician.  I know what a ground is but don't know what a ground "buss" is.  That is a ground to like the frame right?

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Posted (edited)

The ground buss is a common ground point.  Although the airframe could be used for the ground it is not recommended.  Checkout aeroelectric.com and purchase his book and disc for the best buy for info on aircraft electrical.

https://matronics.com/aeroelectric/Catalog/AECCatalog.html

Edited by wypaul

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Posted

What does the common ground point tie to. Seems like ultimately it all ends up back to airframe. 

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Posted

I run a cable from the battery to the ground buss and from the buss to the engine ground.  All of this is covered in the book if you decide to get it.  There are other ways of doing it for sure.

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Posted (edited)

What does the common ground point tie to. Seems like ultimately it all ends up back to airframe. 

Depends. In a glass airplane the battery negative will be terminated to a terminal block (buss) where multiple wires will be terminated. In a welded steel fuselage the negative side of the battery will be terminated at any convenient point on the fuselage near the battery and a ground buss will be located near the firewall also tied to the fuselage. 

Edited by Emory Bored

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