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FX/EX breaker switch failure

frequent_flyer

frequent_flyer

Registered User
Arizona, USA
The EX and FX, and probably many other CC types, use a combined circuit breaker and switch for control of several circuits. Has anyone here had problems with these switch/breakers?

My strobe breaker/switch seems to have failed mechanically after only about 150 hours on the airframe. Switch will not latch up with master off and the feel is very different from the working breaker/switches.

Anyone know the part number - I suspect it's a TYCO W31X2M1G5
 
I use these breaker/switches, Tyco W31X2M1Gx at several different amp ratings, with no problems in my certified Cub. I have 500+ hours on them.

S
 
P/N should be on the breaker, but souinds like you already know that.

While I'm only around 250hrs, breakers have performed without issues. It is the only type of breaker I used when building up my panel.

Maybe swap a breaker to verify it's the breaker and not something else.
 
aeroaddict said:
P/N should be on the breaker, but sounds like you already know that.
Click to expand...

Reading the breaker part number requires removing the GDU 465, dropping out the NAV and STOBE breakers together, reading the part number, then either putting it back together or grounding the aircraft while I wait for the replacement to arrive. I'd rather do the job only once.

I ordered two TYCO W31X2M1G5. That way, if they are not identical to the existing breakers, I can replace both and the lighting bus bar will still bridge them properly.
 
Failure to latch and soft feel verified this morning. Then I dropped the NAV and STROBE breaker/switches out of the panel without disconnecting any terminals. The STROBE breaker now had normal feel, latched properly, and the strobes worked!

I decided not to trust this breaker and replaced it. I don't know why it stopped working in the panel but worked as soon as it was dismounted. Seems to suggest something was mechanically stressing the breaker, possibly the hard copper bus bar that linked the two breakers.
 
I’ve changed a bunch of these- they are a great way to save panel space, but something with the fact that it’s a breaker results in a switch that obviously doesn’t last as many cycles as a normal switch- they also break easily if you catch them with a toe getting in or out... I still use them on new builds- well worth it for the space savings/simplicity...
 
There is a Cessna service bulletin on these breaker/switches. I believe they were standard equipment in some of the 300 and 400 series Cessna twins.

Tim
 
Last week I had to flip my Tyco W31 circuit breaker switch a few times that turns my radio and fuel flow on. Sunday while stuck in the mud and trying to call another pilot prior to him landing it would not come on. When I got back to the airport I removed it and dug in my stash for a replacement. The one that failed was verified with my multi meter and was made in Mexico, the others I had were made in China. I have used these Tyco breaker switch in all my rebuilds and this is the first failure I have had. Know on me I probably used a used switch from my stash of stuff I removed from a rebuild so total time is unknown. Been in service in my plane for the last 4 years. I could feel the difference in the non-working switch.
 
I always gotta know how stuff works and how it broke. Copper braided wire broke in half.
PXL_20210914_180819596.jpg
PXL_20210914_180826784.jpg
 

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Steve Pierce said:
I always gotta know how stuff works and how it broke. Copper braided wire broke in half.
Click to expand...

Thanks for the photos. I'm still trying to understand how the latching mechanism works. It would be easier if I could hold it and play with it. There appears to be an adjustment at the lower left of the first image. The case has a sealed hole at that location. Does this adjustment control the over center latching or the trip current?

I'm surprised the fractured braid would change the feel of the switch. Did it latch on after it failed or drop back to the off position? If it latches can you show a photo of it in the latched On position. I'm curious how all the links line up when it's latched.

Thanks.
 
That sealed plug is a screw that holds that whole brass frame in place. It was like a Chinese puzzle when it came apart with springs going everywhere.
 
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