Replies to This Discussion

Permalink Reply by David Krakowsky on April 22, 2018 at 9:02am

Hi Gil, 

the reason for a switch is in case of an alternator malfunction, you can shut it down. An alternator is capable of putting out  as much as 50 volts and can fry your avionics. Also may help when an electrical fire happens, shutting down the Alternator sometimes helps.

if it did shut off again, you must have a circuit breaker/switch combo. It could be a faulty switch, but most likely something is causing a large current draw, tripping the breaker. Shoot some WD40 or contact cleaner into the switch, sometimes they get corrosion. 

If you have any monitoring or gauges, see what the current or amps draw is. My Dynon 180 shows amps, if all you have is volts, the voltage will most likely be very low when the short is drawing too much.

i would not fly until you resolve the issue.

what kind of alternator and battery do you have.

Post a picture of your switch and panel.

It might help me to understand what you have.

Dave

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Permalink Reply by Jim and Amelia Isaacs on April 22, 2018 at 9:15am

Gil,

Is this a circuit breaker switch? Good discussion here http://www.vansairforce.com/community/archive/index.php?t-125424.html

Jim

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Permalink Reply by Gil DeVault on April 22, 2018 at 4:55pm

I pulled out the breaker this morning. Yesterday when I noticed the problem I reset the switch not knowing it was a breaker as well. Volt meter came back up everything working as before for a few minutes then it shut down again. This morning when I pulled it out. I see it actually is in series with the alternator output, not just the field wiring.  It is a tyco W31-X2m1G-35. Aircraft Spruce has them and I now have one on order. No I won't be doing any flying until I find out if a new one solves my problem. This old one feels sloppy and rough, not a crisp snap you would expect from a snap type switch.  I'll hook up an amp meter in series before I put everything back together. I may just pull the cowl and take the alternator and have it checked out. It is just a 35 amp one wire GM type on an 0-235 Lycoming.. 

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Permalink Reply by David Krakowsky on April 22, 2018 at 6:24pm

Sounds like your heading in the right direction. Let us know what you find.

Dave

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Permalink Reply by Gil DeVault on April 23, 2018 at 11:10am

Took the cowling off, checked all the wires for loose or burnt connections, nothing. Removed main wire from master relay and checked for 12 volts at the relay, everything fine so for. Used aux 12 volt battery to power bus, everything working as should, no smoke or popped breakers. Removed alternator, looks fine, but taking to alternator shop this afternoon to have checked. It is an obsolete Mitsubishi 60 amp, or so I'm told by auto supply house. The rotor spins freely, no drag or bearing noise at all. I'm starting to suspect it is just a corroded breaker, as this plane sat for a few years in an unheated hangar. Luckily the cylinders all checked out, little or no compression loss on any cylinders. I did put a drop of oil in the breaker and hooked it in series with a headlight and it didn't trip. Anyway should have a new breaker in the morning & a checked out alternator. Problem here in the Ozarks, hangar is a 45 minute drive one way, and the only alternator repair shop is another hours drive away. Sometimes living in the Country can be a bummer. 

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Permalink Reply by Ken Ryan on April 23, 2018 at 11:17am

Does your electrical architecture include crowbar over voltage protection? If so, you might want to check that system to see if it might be causing your breaker to trip.

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Permalink Reply by Gil DeVault on April 23, 2018 at 5:03pm

Only protection, circuit breakers and internal voltage regulator in alternator. Alternator checks out OK. Putting our 50 amps on tester. So for everything seems to be OK. I can't check accurately the current, my multi meter only goes up to 10 amps DC. I did purchased a cheap analog amp meter  from auto parts, and it seems to show around a 20 amp draw with everything turned on. after I put a drop of oil in the circuit breaker it seemed to work fine, didn't trip when clipped into circuit. I will still put in a new one when it arrives. Tonight I will look up all of my electrical loads and see just what they should be.

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Permalink Reply by Gary Welch on April 23, 2018 at 11:02pm

Disclaimer - this came from Bob Nuckolls, not me! Anyway, he does talk about the short-comings of circuit breaker switches and their potential for failure. Not knowing any different, I took his advice and didn't use them in my plane. (Well, that, and the fact they were $30 a piece...) You can read his discussion on the subject online, though I don't have the reference right now.

Having said that - most RV's and a zillion other certificated aircraft are flying with circuit breaker switches so this is not necessarily any real issue. Mr. Nickolls, however, has the engineers mentality on some issues... 

The main point being, that it's not unusual for these switches to fail. Not common, but not unusual.

Anyway, don't flame me for the comment and I'm not suggesting anyone shouldn't use circuit breaker switches! 

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Permalink Reply by Gil DeVault on April 24, 2018 at 7:23am

Gary, myself, being an old, old electrician, I can see the good and bad points of each a breaker, switch, and fuse. When first going to trade school in the sixties circuit breakers were not as common in the housing and industrial areas as fuses. The reason give to me was the fact with a fuse you have a fault, you repair it with a new fuse. A breaker is mechanical, and as with all mechanical parts they wear out over time. One would think that would be the end of the story, but it isn't. As you mentioned in most aircraft there are more breaker/switches than fuses. The same is true in homes& industry. It is almost impossible to buy a Buss screw in fuse box or fuses anymore. In the 601 I am building I elected to go with fuses. One because of the cost factor, and I have put one on each electrical item in my plane properly sized. This is one where it is perfectly acceptable to go either way in my opinion as a retired electrician.

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Permalink Reply by Gil DeVault on May 8, 2018 at 5:04pm

I was able to replace my W31-X2m1G-35 circuit breaker on my alternator output.  While waiting on my new circuit breaker I took off my alternator and took it to an alternator shop to have it checked. Turns out it is an alternator manufactured for use on industrial fork trucks. It is rated at 60 amps. It also checked out under load on the mechanics fixture. I then removed my top cover over the panel and checked out everything, wiring for loose connections, burnt wires, anything visible. Everything I checked looked ok with the exception of the breaker itself. I checked the current draw with everything on, as best I could with an old analog amp meter and it looks like I am drawing around 20  continuous amps. The breaker is rated at 35 amps. The nav lights are the largest user of power, but as a Light Sport I will never use them or the landing light unless it is an emergency. Anyway I flew today for little over an hour with everything on and no problems. Pretty sure it was the breaker which seemed a little corroded to me. 

Gil

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