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  #11  
Old 12-28-2014, 07:48 AM
RVDan RVDan is offline
 
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Curious, what type of wire was used- M22759 (AS22799) or other?
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  #12  
Old 12-28-2014, 08:45 AM
todehnal todehnal is offline
 
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Location: Kentucky Lakes area in KY
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Hey Him,

So sorry for your troubles. Sure hope that the damage is limited to the area that you mentioned, and that repairs go well for you.

If you get a chance, a few pics would sure be helpful in providing a better understanding of the problem. There is a lot of talent on this forum, and actually seeing this area just might offer some additional insight.

Tom
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  #13  
Old 12-28-2014, 09:26 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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Quote:
Originally Posted by JRo View Post
It is "hot" whenever the master switch is on.
Correction
It is only hot when the start key is turned and the engine is cranking with the starter motor.
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  #14  
Old 12-28-2014, 09:49 AM
RFSchaller RFSchaller is offline
 
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I have a fuse position marked "START". I thought that protected the starter relay circuit. There was an old thread that recommended going to a 3A fuse versus 2A due to the fuse blowing.
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  #15  
Old 12-28-2014, 10:24 AM
Mich48041 Mich48041 is offline
 
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It seems that JRo is describing wire P157-12-43 which is the main unfused feeder from the battery that powers the aircraft. From JRo's description, it sounds like that wire shorted out to the choke cable.
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  #16  
Old 12-28-2014, 01:28 PM
BigJohn BigJohn is offline
 
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Location: Gloversville, NY
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Quote:
Originally Posted by Mich48041 View Post
It seems that JRo is describing wire P157-12-43 which is the main unfused feeder from the battery that powers the aircraft. From JRo's description, it sounds like that wire shorted out to the choke cable.
That is correct Joe. I have photos and will post them at some point, when appropriate, with JRo's permission.
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Last edited by BigJohn : 12-28-2014 at 01:31 PM.
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  #17  
Old 12-28-2014, 02:24 PM
JRo JRo is offline
 
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Location: Poestenkill, NY (near Albany)
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The wire in question is WH-P157, battery power wire (white). And it is always "hot" with the master switch on, not the starter. It is a #12 wire. It apparently shorted out in my case, causing an extreme heat source. In fact, it got so hot that about 6" of wire simply "vaporized"! It is extremely important to note that this cable was not fused or protected in any way. Almost always throughout the industry, cables of this type are protected by a fusible link, which will, by design, fail internally and cut the current in case of an extreme overload, such as a short. Without such protection, the extreme heat will continue until the wire melts away (as it did in my case) or until the current is switched off.

Based on what I know now, I would strongly advise installing a fusible link on the battery power wire in the RV-12, as well as any other big-draw circuits that are not already protected in some way.

Several of you mentioned the issue of an engine-to-fuselage ground. Although it's a realistic concern, it was definitely NOT the case with my plane, as I long ago took the precaution of adding a very solid & substantial ground wire from the top of the right rear cylinder (where there's already a tapped screw hole) to the fuselage nearby.

Thanks,

JRo
N448JR
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  #18  
Old 12-28-2014, 02:51 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by JRo View Post
Almost always throughout the industry, cables of this type are protected by a fusible link, which will, by design, fail internally and cut the current in case of an extreme overload, such as a short.
Some industries this may be the case, but not light aircraft.
There are tens of thousands of Cessnas and Pipers (and others) configured the exact same way. I imagine the majority of RV's are also.
I am not arguing that a fuse-able link is not a good idea, just saying that there is nothing standard about it (in general aviation light aircraft anyway).

Sorry to hear about your incident, but glad that it looks to be rather minor.
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  #19  
Old 12-28-2014, 03:21 PM
hthaman hthaman is offline
 
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Location: IA
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Quote:
Originally Posted by JRo View Post

I long ago took the precaution of adding a very solid & substantial ground wire from the top of the right rear cylinder (where there's already a tapped screw hole) to the fuselage nearby.

N448JR
would you put a pic of this connection please ? Any recommendation from VAN's ?

thanks
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  #20  
Old 12-28-2014, 03:27 PM
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Sam Buchanan Sam Buchanan is offline
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Location: North Alabama
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Quote:
Originally Posted by JRo View Post

Based on what I know now, I would strongly advise installing a fusible link on the battery power wire in the RV-12, as well as any other big-draw circuits that are not already protected in some way.
Not to pile on your already unfortunate experience, but standard practice is to route/protect the fat wire so it can't chaff against the choke cable (or anything else)?

Fusible links usually aren't used in this location because a momentary spike or defective fuse can take down the entire system.
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Last edited by Sam Buchanan : 12-28-2014 at 03:38 PM.
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