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Alternator problem-----and the solution :)

Mike S

Mike S

Senior Curmudgeon
Today while returning from taking a buddy to Watsonville, ( apx 45 minute flight) the alternator warning light on the panel started blinking, and I noticed the field breaker on my RV 10 had popped. I tried resetting it, no joy. Then, tried turning off master, breaker in, and when the master was turned back on, pop goes the breaker.

Luckily I have a backup alternator and backup battery, so flew home with no problem.

Upon landing, I tried cycling the breaker again at idle, just in case it was a high RPM induced issue-----Master off, breaker in, soon as I turned the master back on again, the breaker pops out.

Then after engine shut down I tried a third time with the same results, when the master is turned on, the breaker pops.

Before I dig into things, anybody out there have any ideas as to what could be the issue???

Thanks in advance.

60 amp B and C alternator, and B and C regulator, apx 240 previously trouble free hours. One more tidbit, on the flight to Watsonville, ATC was saying my radio was scratchy and virtually unreadable. Both radios exhibited the same noise on transmission.
 
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Download the B&C troubleshooting sheet. That will narrow down the problem.

I had a similar intermittent problem. A loose connection at the alternator created an over voltage event and would trip the field breaker.

My guess is that you are having an over voltage event and are tripping your over voltage set point that exists in the B&C voltage regulator.

By using the B&C Troubleshooting sheet, that will narrow down where your problem is located.
 
Look under the hood

Perhaps this isn't electrical, but rather mechanical. Same thing happened to me a month ago. Found that the alternator had seized, spun the nut off the shaft. Alternator pulley was free-wheeling, and the belt was hanging behind the flywheel. Belt was damaged, and at that point I became aware that you don't just replace the belt like in your car. Anyone know how to stretch the belt over the prop?

If anyone in Indiana finds that nut, it's mine.

Jim
 
Old rule Mike, reset a breaker one time. :)

If it keeps on tripping something is not right and resetting it won't fix it. The reasoning behind the rule is something could be getting hot and a fire would not be good.

Good luck in finding the cause, I have no idea what it might be except a short to ground somewhere or a loose connection.
 
It is not an over-voltage problem because the breaker trips with the engine off and the alternator not producing power. Something is shorting to ground. A wire, or O.V. module, or voltage regulator, or alternator field?
Joe
 
No smoking allowed . . .

Mike S said:
Clue #1. Then after engine shut down I tried a third time with the same results, when the master is turned on, the breaker pops.

Clue #2 . . . . . ATC was saying my radio was scratchy and virtually unreadable. Both radios exhibited the same noise on transmission.
Click to expand...

Mich48041 said:
It is not an over-voltage problem because the breaker trips with the engine off and the alternator not producing power. Something is shorting to ground. A wire, or O.V. module, or voltage regulator, or alternator field?
Joe
Click to expand...

+1 As a young Service Writer I had a mechanic that was exceptionally quick in finding shorts in wiring. After 4-5 jobs I assigned him, I went over to him to find out how he did it. Sheepishly, he showed me, afraid he would be admonished for his process. He took a heavy wire from the battery and touched it to the shorted wire. Left it there for a short time then felt the wiring harness for the heat, following it down the harness, if it suddenly became cool, he found the point of the short. If the wire was shorted too long, of course it would get too hot and smoke, so I dubbed this the "follow the smoking wire" technique.

Regardless whether you use at your own risk, discard completely, or see the brilliance in it's simplicity; it might give some insight to finding your short without smoking (a wire).
 
Thanks gang !!

Thanks to all who have taken the time to respond, Gary-----the link to the troubleshooting guide is very much appreciated, I had no idea there was such a thing.

I am pretty sure it is either a loose connection, or a short---------due to the fact it happens even with the engine off. I described all the various things I tried so as to cover all the bases info wise------------with electrical stuff the rabbit chasing can be rather excessive due to false clues or lack of pertinent ones.

Gonna go crawl/wiggle/contort etc under the panel and start looking for gremlins-------then pull the cowl if needed and continue the search.

Keep the ideas coming, all thoughts are appreciated.

Will report back when I have this particular snake taken care of.
 
As a car mechanic

i would not wiggle or shake wiring keep short shorted! For now. Because if you disturb wiring short may disapear.
Disconnect field wire from alternator and see if it pops the fuse if not
Check alternator field for shortage something tells me brushes shorted
 
Disconnect wire at field terminal on the alternator. Apply power. If breaker pops then disconnect field wire from regulator. If breaker still pops its a wire short if not then it's the regulator..
 
It sounds like a short to me too. Does it pop with the engine off as well? Try running a new wire from the breaker to the alternator outside the airplane (or regulator) and see if it works right (you could run it out the air vent so you can close the door). If so, there's a short in the file wire somewhere.
 
Jesse said:
Does it pop with the engine off as well?
Click to expand...

Yes, it does. Seems to pretty much eliminate the over voltage issue, as I see it.

I am also leaning toward it being something shorting-----

Bill.Peyton said:
Disconnect wire at field terminal on the alternator. Apply power. If breaker pops then disconnect field wire from regulator. If breaker still pops its a wire short if not then it's the regulator..
Click to expand...

Bill, excellent advice-----this is the kind of suggestion I was looking for-------VAF brain trust at work.
 
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Bill.Peyton said:
Disconnect wire at field terminal on the alternator. Apply power. If breaker pops then disconnect field wire from regulator. If breaker still pops its a wire short if not then it's the regulator..
Click to expand...

Been reading and thinking about this---------the breaker is popping when the master is switched on, not when the field is switched on. Cessna type split switch.

The field half of the switch is still off and the breaker is popping------thus the problem should be between the breaker and the field side of the split switch-----------------yes??

Or, am I missing something here.
 
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And the gremlin is.........................

Well, for anybody following this thread--------------I have found the problem,

Mike S said:
The field half of the switch is still off and the breaker is popping------thus the problem should be between the breaker and the field side of the split switch-----------------yes??
Click to expand...

When I built the new panel to accommodate the new 8.4" GRT screens, I had to move almost everything a bit closer together from how stuff was laid out for the 6" screens.

Turns out the housing of the key switch hit an unused tab on the field side of the Cessna split master.

The real culprit here is the fact the key switch is designed to use an indexing tab to keep the switch housing from rotating----------and I did not take the time to install one.

So, rotate the switch back where it belongs, install a device to keep it there, problem gone.

My bad, mea culpa, loose nut behind the wheel, operator induced failure-------:mad:

The real take away from all this is---------------I did not just start looking at the issue of a bad alternator and pull the cowl, start tracing wiring, and generally driving myself nuts with following rabbits down holes. I asked for input from the good and knowledgeable folks here, and through the feedback I received, I was able to analyze the situation and target the real issue rather quickly.

Thanks to everybody who responded, you all deserve a pat on the back.
 
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Mike S said:
Well, for anybody following this thread--------------I have found the problem,



When I built the new panel to accommodate the new 8.4" GRT screens, I had to move almost everything a bit closer together from how stuff was laid out for the 6" screens.

Turns out the housing of the key switch hit an unused tab on the field side of the Cessna split master.

The real culprit here is the fact the key switch is designed to use an indexing tab to keep the switch housing from rotating----------and I did not take the time to install one.

So, rotate the switch back where it belongs, install a device to keep it there, problem gone.

My bad, mea culpa, loose nut behind the wheel, operator induced failure-------:mad:

The real take away from all this is---------------I did not just start looking at the issue of a bad alternator and pull the cowl, start tracing wiring, and generally driving myself nuts with following rabbits down holes. I asked for input from the good and knowledgeable folks here, and through the feedback I received, I was able to analyze the situation and target the real issue rather quickly.

Thanks to everybody who responded, you all deserve a pat on the back.
Click to expand...

I see a rivet in your future. :)
 
I recently did a panel upgrade and the breaker bank, apparently, was a little too close to the scat tube running up to the vent hole in the panel. The owner said his alt field was popping from time to time. Turns out the lead on the breaker would sometimes touch thermite in the scat and pop the breaker.
 
Mike S.
Good going fixing the short circuit. Did that also fix the unreadable radio transmissions?
Joe
 
Mich48041 said:
Mike S.
Good going fixing the short circuit. Did that also fix the unreadable radio transmissions?
Joe
Click to expand...

Don't know, haven't actually done the fix yet---------still chewing over the method of locking the key switch in place. I have at least 3 options I am looking at----------and the simplest is the one I have the least confidence in.

At the moment, I think the radio thing was a bit of a red herring:confused:
 
Mike S said:
Don't know, haven't actually done the fix yet---------still chewing over the method of locking the key switch in place. I have at least 3 options I am looking at----------and the simplest is the one I have the least confidence in.

At the moment, I think the radio thing was a bit of a red herring:confused:
Click to expand...

To lock the keyswitch in position:
You'll see a groove in the switch body that would normally engage into a tab in a specially punched panel hole. Unfortunately, we normally drill this hole, so we don't have an anti rotation tab.

Instead, in the panel location that you would normally want this anti rotation tab, file a small slot. Then cut a small piece of 14 AWG copper wire from a piece of Romex, just long enough to fill this slot and engage in the groove of the switch body. Hold your tongue in the right position, slide everything into place and tighten.

This copper 'pin' will now prevent the rotation of the switch body
 
Thanks

Vern, the filed slot is one of the ideas I am cogitating over---------had been thinking of making a key out of .060 alum to match the panel, hadn't thought of using copper wire.

Any issues with copper and alum in contact ---------somewhere I seem to remember that they have a bit of galvanic issues. Also, copper seems pretty soft/weak to withstand the sheer load???
 
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First step in my trouble shooting matrix

Is to determine what I was personally involved in with any system or assembly. Seems that most of the time it is something i goofed up that is behind the failure.:rolleyes:
 
Make a tab from a piece of scrap and flush rivet it to the back of the panel. Put another scrap piece at 180 degree clocking to neutralize the offset. The switch trim plate will hide the flush rivet head.
 
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