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Engine capacitor vibration damage


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Just a quick FYI,

 

Here is something most never see and most probably never look at from time to time. This is the 25V 22k ohm capacitor that Rotax 912 engines have in place. This one is a little smaller than the average one so if yours is a little taller that's just fine. For the CT guys it is located and mounted to the square tube engine mount bar up above the battery. Inward on that bar about 10"-12" you will see this wire tied to the back or bottom of the engine mount tube. Other 912's aircraft also have them, but you'll need to find where it is mounted. It usually holds up very well, but can have the leads break off from vibration. You can not re-attach these and will need a new capacitor. CPS sells them for about $25. You can and it is much easier to just re-use the broken off connectors. Just use a soldering gun to remove the old solder and the broken off tip from the capacitor. Then re-solder the connectors back on. Put a small 3/8" piece of heat shrink on the connector just like you found it. leave the top 40% or so exposed. When you re-install the capacitor take note that this is POLARITY SENSITIVE. It has a white strip with a negative symbol along one side. That is the ground wire which is a single wire and has blue heat shrink on it from the plane side. The double plug connector is positive. If you swap these two and start the engine you will need to call CPS again and buy another capacitor as it will burn this one up. Just wire tie the capacitor back either to the tubing or to as vibration free spot as possible. This is a very easy job to do.

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I was surprised at this unorthodox soldering of spades to the pins on this little cap. The pins are not designed for this sort of use and are prone to fatigue. So long as you are swapping it out, you should consider a much more substantial cap (Rotax merely says 22mF minumum) This one is 100mF with solid screw down connections and higher ripple current. Does much better tamping down transponder noise and such,

http://ctflier.com/index.php?/topic/1735-the-sum-of-all-changes-electrical/page__hl__%2Belectrical+%2Bchanges

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Looked at another CT at my field yesterday and found a second broken lead on a capacitor.

I have replaced a few of these over the last couple of years.

 

 

Kurt,

 

Can you find us a good source for the standard capacitor they use and then possible another source for the screw on lead type, but not too big. Something relatively small for the screw in one. Maybe less than 50mm long?

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Rotax very loosly specifies this part. It's a bit like a mechanical engineer saying: just use some sort of screw with 4-40 threads. What you want is computer (AKA long-life) grade aluminum electrolytic. At least 12Amp RMS rated. 105C temperature. Here is one easier to fit, but capacitance is proportional to volume and the more capacitance, the better filtering (stiffening for you audio types)

http://www.newark.com/epcos/b41580a5479m/capacitor-stud-mount-25v-47000uf/dp/18T7242

 

There are none as little as the one that FD uses but that one is both mechanically and electrically vulnerable to failure.

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I used to get this one

 

about same length of the one in CT but bigger AND with screws

 

I can't get them (locally) anymore...but in USA , that should'nt be a problem

 

 

but...the # CGS223U025R2C is 1 3/8'' diam x 2 1/8'' long

 

if you find some,,I 'm in..

post-112-0-29989400-1363728281_thumb.jpg

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FYI,

 

I looked forever for these. I have found them and should have a handful here in 4 days. They are 25v 22000uf 105C.

30mm diameter, 47mm long with a contact spread of 10mm. Perfect for an exact replacement.

 

Hi Kurt,

 

I'm sure the others may have been a good and or better replacement, but they were just so big trying to fit in some planes.

I appreciate your help.

 

Thank You

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No problem. If you want a direct replacement

http://www.digikey.com/scripts/dksearch/dksus.dll?FV=fff40002%2Cfff80009%2C34007c%2Cfc01ea&k=capacitor&vendor=0&mnonly=0&newproducts=0&ptm=0&fid=0&quantity=0&PV252=42&PV252=26

Any of these snap in ones will do. ~$6 but not really adequate if the battery goes. Would need to keep the power below 60W or so (don't run the landing light).

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Could someone please describe the piece where this capacitor sits?

 

I have a 2005 CTSW. And now that I read the physical size of the capacitor, I don't know how I could have missed seeing it when I looked the other day. I think that know where one might have fallen out of though. Sorry for not providing a picture, but my plane is hangared 50 minutes driving time from home.

 

Thanks to Roger and everyone else for making this site such an asset to the CT community!

 

--Mark

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Hi Mark,

 

The capacitor is on the battery side. It is usually wire tied on the backside of the square metal engine mounting bracket above the battery about 8"-12" to the right. It may be inside a piece of fire sleeve for protection. It is 45mm (1 3/4") long and 30mm (1.3") wide.

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Hi Roger,

 

Based on your original post, that is the area where I was looking. Having read some of the later posts, I am surprised that I missed something 30 mm in diameter.

 

I asked about what the capacitor rests in because there is a black plastic piece mounted near the "Ducatti" box above my battery that is about 1-2 inches square with a bunch of what look like electrical pin connection holes on the top. But, there are no wires in any of the connection holes. There are wires running into the bottom of the piece. Also, the bottom of the black plastic piece looks like it should surround round (not square) tube. But, it is not attached to a tube which seemed strange.

 

My plane is a very early 2005 unit. There is another CTSW nearby that is also an early 2005. The other owner and myself have noticed a number of minor differences between our planes even though they only differ by three in serial number. So, I wouldn't be surprised if what I am looking for is not exactly where it is found on most later CTSW /CTLS models. Also, my plane was used by flight school before I bought it. So, there was plenty of opportunity for the capacitor to "disappear".

 

Again, my apology for not thinking of taking a picture when I had the cowl off. Thanks again for the help!

 

--Mark

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Jacques, thanks for the picture!

 

I will recheck the square engine mount bar...but the only thing that I remember attached to that square bar was the BRS bridle. Maybe it was hiding under the air duct to the right carb.

 

I don't see the plastic item that I was referring to in this picture. The plastic item that I saw is sort of "suspended" in front of the silver piece with the cooling fins (black electrical connector on its rights side) and above the negative terminal for the battery. I say "suspended" because the electrical wires to it seem to be its only attachments.

 

I asked because I am having some intermittent electrical issues. Last time I was at my hangar, I tightened the bolts through the firewall to the rectangular silver piece and the round brass piece. Unfortunately, the weather that day did not allow for a few trips around the pattern.

 

Thanks again guys...

 

--Mark

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I made the drive down to my hangar today. With Jacques picture in my mind, I opened the cowl to find the capacitor right where it was supposed to be.

 

To paraphrase an old friend from high school...there are no so blind as those who don't know what they are looking for...

 

Thanks,

 

--Mark

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  • 9 years later...

I just noticed this lead broken and found this thread discussing it.  What does this capacitor do ?  There was nothing in regards to aircraft operation that was wrong or at least I didn’t notice anything - it was  just by chance I was inspecting and saw that wire not connected (negative wire)   Oh and any newer info on where we can get replacement ? Thanks 

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050CBB3C-2FB1-4FBF-9A7E-D50B12C22C90.jpeg

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