What happened?

EdFred

EdFred

Taxi to Parking
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Feb 25, 2005
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White Chocolate
So I'm crusing up to 6Y9 on Friday evening, and about 25 minutes from destination my brother notices the amber light on the Volt-Ammeter indicating a discharge. Battery is holding a charge ok, but instead of normally showing 20-30A of load on the alternator, it is now showing -4.5A of discharge. I start switching everything off and back on to see what the culprit may be. No joy. Nothing at all. Cruise on in just before dark - not sundown - DARK, into the unlit strip (no worries, the trees are MUCH darker than the grass) and shut down for the night. Try and troubleshoot on Saturday, and I'm crawling up under the panel with the multi-tester, and I'm checking everything behind the panel. Still no luck. Battery still holding full charge, and the ammeter now shows 0.0A when the engine is at idle, or up to 1500RPM.

What happened to cause this?

(First correct answer gets a free burger at the fly in on Aug 5th - I found out the problem this morning.)
 
You are making it sound simple (no "and then they yanked the VR, the alternator, woe i$ me") so my first guess is the alt circuit fuse/CB.
 
It's hard enough to troubleshoot something when your looking at it! :dunno: Doing it over the internet is a real trick:yes:
 
Something extremely simple...so simple that you don't even consider it....You eventually figure it out.....Wonder why you didn't think of that....and wonder if anyone else would have?
 
The alternator kept charging the battery. It was night. I had on the transponder, GPS, radio, nav lights, panel lights, landing light, fuel pump (on descent) strobe/beacon, turn coordinator all running, and the battery was full power upon landing.

I know someone will get it. It was the 3rd thing I checked. (counting looking under the panel as one thing - I checked more than one thing when down there.)
 
Let'sgoflying! said:
you bumped the alt switch off
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*sigh* If the alt switch was off, I'm pretty sure the battery would not charge - and I only have a single master switch.
 
One step at a time. Alterantor belt okay? Alternator wires not disconnected. Move to step two.

Check battery system, no shorts or grounds in the system. System must of been okay to start engine. Starter system Okay engine started. On to step three.

Lets see battery to the battery switch, to the master switch, to the alternator field circult breaker to the pull on alt switch, to the primary buss. So it sounds like the alternaor field circult wire was off if you get no amps at idle, wire went to ground or a bad amp meter depending on your eletrical system. Or the alternator control unit ground is bad, which would isolate the alternator system.

I assume all is fine with battery power on? What did the voltage read at idle?

This is why troubleshooting costs so much when a mechanic has to check each system one step at a time. As of now I am looking at the alternaor control side as the problem if the amp meter is working okay.

Stache
 
Maybe the Radio interference capacitor short, Do you have a test button? that could be bad or pushed.

Bob
 
Flux capacitor went into reversionary mode inducing a osmotic overpressure on the alternator fill tube. Or like Ev said....could be aliens. All this administrivia trying to figure out what switch you turned off is making my head hurt. Maybe it's just a hangover.....or aliens.
 
Col. Mustard...



in the study...



with the candlestick!
 
It's entirely my fault; I jinxed it by not having returned your telephone call of 5:35 PM, Friday, May 26, as indicated on my home caller ID.

So sorry, Ed; I was on my way back from Portland Jetport -- via DiMillo's Floating Restaurant -- with Her Majesty. And we've been running since then, what with family memorial(s) in three towns, perennials and plants for my flower garden, flowers for the burial site/head stone in my back yard[Darrell, the yellow kitty died :eek:( ]. Oh! And you wouldn't believe the house; the amazing transformation having taken place re the previously unplaced furniture and art works from Arizona.

Sorry about your plane problem; and I'll get a set of my Ed's Trip To Maine photos out to you in a day or two.

HR
 
I'm just gonna guess here: Did you leave something plugged into the cigar lighter that was drawing a whole lot of power out?
 
OK, so you have told us that, notwithstanding the ammeter indications, the battery was, in fact, accepting a charge and that the alternator was delivering the charge.

And there was nothing wrong behind the panel.

So, what, maybe a dirty connection at the ammeter shunt bar? Does your plane have such a critter? Something in the ammeter sense circuit, if the actual business of charging continued unabated...
 
SCCutler said:
OK, so you have told us that, notwithstanding the ammeter indications, the battery was, in fact, accepting a charge and that the alternator was delivering the charge.

And there was nothing wrong behind the panel.

So, what, maybe a dirty connection at the ammeter shunt bar? Does your plane have such a critter? Something in the ammeter sense circuit, if the actual business of charging continued unabated...
Click to expand...
Bad master switch.?
 
N2212R said:
The problem was not under the panel.
Click to expand...

Ed, your description has me a bit confused. Most simple airplanes have either an ammeter connected between the battery and the main bus or a loadmeter connected between the alternator and the main bus. An ammeter has the zero at top center and can show a charge (positive current direction) or discharge (negative current direction) of the battery. A loadmeter OTOH indicates alternator output which is always positive and therefore has the zero at the left (low) end of the scale. Now it is true that a loadmeter is really an ammeter, but IME those two names have the specific meaning I stated, at least in aircraft electrical systems. Granted there are a few experimentals out there with an ammeter (zero center) gauge connected as a loadmeter but I wouldn't expect to see that on a certified airplane in airworthy condition.

In your first post you stated that the ammeter was: "normally showing 20-30A of load on the alternator, it is now showing -4.5A of discharge." A properly connected ammeter shouldn't show 20-30A of load, like a loadmeter would, but rather an ammeter would normally show a slight positive (charging) current on the order of an amp or so (this current is actually the battery float charge current plus the current flowing in the coil of the master contactor). Conversely, baring an instrument malfunction or a short in the alternator or it's wiring, a loadmeter should never show a discharge even if it could and a mechanical one with the zero on the left couldn't show a discharge even if there was one.

This plus your mention of an "amber light on the volt-ammeter" leads me to believe that you have an aftermarket electronic voltmeter/ammeter combination gauge and I'm not at all sure how it's wired in. I am wondering if it is actually a three function gauge that can display bus voltage, alternator output, and battery current and if so, I'm not sure what the indications were of those measurements. Perhaps if you explained your unusual electrical system and/or exactly what the "volt-ammeter" read in it's various modes it would be a little easier to guess what the trouble was.

From what you have posted, it appears that your alternator was working which rules out it, the regulator and associated wiring (there's no way the battery voltage would remain at the normal level of 14/28 volts with any significant loads unless the alternator was working). That means the gauge itself was incorrectly sensing something but without a better idea of exactly what that gauging setup is it's awfully difficult to tell what went wrong. That said, my first guess would be that the volt/amp selector itself was mispositioned or malfunctioning if it weren't for the glowing amber lamp indicating a detected fault.
 
I'm still confused by the negative discharge, after I re-read in my owners handbook that it shows the amount of load the alternator needs to supply - while it shows amperes, it is actually a load meter like Lance guessed. So before I took off yesterday morning to come home, I pulled off the top and bottom cowls - looked at the alternator, and there was the culprit: The ground wire to the alternator was broken off right at the ring terminal. Without the 0 reference of the ground wire the loadmeter had nothing to measure the current against, so it was then showing 0A. My guess would be that the negative discharge may have been caused by the ground wire flopping around inside the compartment near the alternator, and perhaps measuring a higher charge somewhere near the alternator, measuring it back against the charge being used by the electrical system, and showing a discharge. When I had it in idle and run-up on the ground (so to speak) it showed 0A. Stripped a little insulation off the end of the ground wire, got a ring terminal from a guy I know in town, crimped it back on, started it up, and voila. A simple fix.

Then, after talking with my uncle this morning and seeing his confusion, I remembered that the Beech Sierra has a plus - minus ammeter which you always want at 0A. I then realized I did not provide enough information for the challenge, sorry.
 
N2212R said:
I'm still confused by the negative discharge, after I re-read in my owners handbook that it shows the amount of load the alternator needs to supply - while it shows amperes, it is actually a load meter like Lance guessed. So before I took off yesterday morning to come home, I pulled off the top and bottom cowls - looked at the alternator, and there was the culprit: The ground wire to the alternator was broken off right at the ring terminal. Without the 0 reference of the ground wire the loadmeter had nothing to measure the current against, so it was then showing 0A. My guess would be that the negative discharge may have been caused by the ground wire flopping around inside the compartment near the alternator, and perhaps measuring a higher charge somewhere near the alternator, measuring it back against the charge being used by the electrical system, and showing a discharge. When I had it in idle and run-up on the ground (so to speak) it showed 0A. Stripped a little insulation off the end of the ground wire, got a ring terminal from a guy I know in town, crimped it back on, started it up, and voila. A simple fix.

Then, after talking with my uncle this morning and seeing his confusion, I remembered that the Beech Sierra has a plus - minus ammeter which you always want at 0A. I then realized I did not provide enough information for the challenge, sorry.
Click to expand...

That's what I was going to guess. :D

Do we all get burgers?
 
I had the field wire break off inside the ring terminal insulation on the back of an alternator on a Cardinal one time. On the ground and in climb the alternator worked...in cruise it didn't. Couldn't find the problem til I started tugging on the individual wires in the wiring harness. It appeared the field wire was too taut when installed after the alternator had been replaced recently and the strain coupled with the engine vibration caused the failure.
 
Lawreston said:
Yeah! And I'm so glad it wasn't my fault.

:eek:)
Click to expand...

Actually what I was calling you about was that I couldn't find my checkbook, and I thought maybe it fell out of my yellow computer bag when I was at your place or in your car. After I got home, I found it in my red travel bag. I know it was in the yellow bag at one time, and I must have swtiched it when I was on Martha's Vineyard. Probably good, I DIDN'T get hold of you, or I would have had you needlessly looking for something that I was in possession of.
 
N2212R said:
Actually what I was calling you about was that I couldn't find my checkbook, and I thought maybe it fell out of my yellow computer bag when I was at your place or in your car. After I got home, I found it in my red travel bag. I know it was in the yellow bag at one time, and I must have swtiched it when I was on Martha's Vineyard. Probably good, I DIDN'T get hold of you, or I would have had you needlessly looking for something that I was in possession of.
Click to expand...

So I take it the problem with your amp meter/yellow light was the fact that your checkbook was in your red travel bag.. and not your yellow computer bag.

I guess then as long as I don't carry my checkbook in a red travel bag I'll never have to worry about alt/bat problems. Of course I don't have to worry about it anyways.. considering my travel bag is "BLACK!"

Dakota Duce

"May All Your Flights Be Of Good Weather!"
 
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