Electrical failure/switch failure

vlittle · #1 10-06-2006, 06:35 PM

I've just experienced my second and possibly third switch failure in 95 hours.

On my first flight, my master switch failed... leading to overvoltage alarms. It was intermittent, and it took me a while to diagnose. B&C replaced the switch, and I sent them the failed switch for analysis.

Last week, my Strobe breaker kept popping when I switched the strobes off. Today, I went into diagnosis mode and found:
- Strobes did not work.
- Breaker was permanently open.
- Nylon insulation on the fast on terminals at switch were burnt black.
- Brass switch terminals were discolored.
- switch terminal rivets were loose (same failure as Master switch).

I tested the failed B&C (Carling) switch at home with a power supply in current-limit mode (5 amps) and it got quite warm. I measured the voltage across the terminals and got widely varying measurements as I wiggled the terminals.

Conclusion: switch failure.

Yesterday, I also had a flap system failure... I suspect a switch problem as well, but no conclusion yet.

Anyone else seen these failures with the B&C sourced Carling switches?

Vern Little

Captain_John · #2 10-06-2006, 06:44 PM

This switch?

I wouldn't install this switch on my lawnmower!

I googled up what you gave me and that is what popped up.

This is the page I saw:

http://www.sbw.org/switches/

Specifically, what switch are you using, Vern?

CJ

vlittle · #3 10-06-2006, 08:31 PM

I'm using the Carling toggle switches with riveted terminals.

See this link

Vern

Captain_John · #4 10-09-2006, 06:49 PM

Vern, That LOOKS like a quality switch!

It comes at a good price of only five bucks, but there is no information as to it's amp rating.

Also, B&C usually has good quality stuff.

What is the Rating on the switch?

I bet B&C would want to know that the swich has been failing for you. Perhaps they have an answer.

Send them an email and tell them so. If you don't get satisfaction, I will post it on the aeroelectric list for you. I just HATE email based forums.

Lemme know. I was thinking of using those very switches!

CJ

vlittle · #5 10-09-2006, 07:29 PM

Quote:

Originally Posted by Captain_John

Vern, That LOOKS like a quality switch!

It comes at a good price of only five bucks, but there is no information as to it's amp rating.

Also, B&C usually has good quality stuff.

What is the Rating on the switch?

I bet B&C would want to know that the swich has been failing for you. Perhaps they have an answer.

Send them an email and tell them so. If you don't get satisfaction, I will post it on the aeroelectric list for you. I just HATE email based forums.

Lemme know. I was thinking of using those very switches!

CJ

Yes, I've been in touch with B&C to resolve. These switches are rated at 15A, 125 VAC, and should be good for the same current at 12VDC.

B&C did have a problem with Chinese manufactured Carling switches, but have pulled the supply of these. My switches are made in Mexico. Also, an avionics tech told me that I should solder the rivets to provide more mechanic al strength, but I still want to chase down the root cause.

Vern

Captain_John · #6 10-09-2006, 07:39 PM

Hmmmm,

I would not solder the rivets. Introducing heat is probably not going to anything good.

I have had the opportunity to tinker with the ones Van sells and they seem REALLY nice!

Maybe swapping them out would be the best option.

As far as the strobe breaker popping, is there any way you can ascertain if it was a ground fault or overcurrent causing the problem? Those are the only 2 reasons for a CB to trip.

CJ

Captain_John · #7 10-09-2006, 07:48 PM

WHOA Vern,

I see this is getting some serious press in the aeroelectric forum already!!!

Lemme read up on that one over there.

CJ

Mike S · #8 10-10-2006, 09:25 AM

Quote:

Originally Posted by vlittle

. These switches are rated at 15A, 125 VAC, and should be good for the same current at 12VDC.

BVern

You might be surprised.

D.C. current ratings are much lower than A.C.

Check, dont assume.

http://www.aeroelectric.com/articles/swtchrat.pdf

Mike

vlittle · #9 10-10-2006, 09:33 AM

See this link Switch Ratings

To summarize: "In a nutshell, 125 VAC ratings equate favorably and
conservatively to 14 VDC ratings - as long as the switch has
a healthy "snap" action . . . all toggle switches and most rocker switches do."

I have no reason to doubt the information.

V

Mike S · #10 10-10-2006, 09:46 AM

Vern, interesting that we both cite the same work, but diferent parts of it.

In a prior paragraph, it says that D.C. ratings sometimes have to be de-rated by as much as 75%-----------what I was refering to.

I have bumped into this before, and I know from experiance that the D.C. capacity of a switch is less that the A.C.

Been there, done that.

I was not aware however of how much of the reduction is related th the TYPE of load--------as shown in the chart in the link.

Perhaps some electrical engineer type out there can add a bit of clarity here?? Stein??

My guess is that the answer is going to be something along the lines of "Well, you are both correct----but------"

Anyway, good luck in finding the problem, and keep us informed please.

Mike