What is causing my electricals to reboot?

Do you have a solenoid tied to an avionics master. When my solenoid started acting up, PTT could cause the avionics to shut down. I replaced the solenoid and all is well.
 
If I'm reading that table right, you started with a fully charged battery from being on the tender in the hangar and after two legs the battery had fallen nearly over two volts.

Your charging system isn't working in the aircraft. Another leg and he battery would be down to 11.something volts and keying the radio would cause a voltage drop that would have dumped the entire panel again.

Confirmation: You started it at something below 13.8 or so and never saw anything but "slight charge" on the ammeter.

Or the battery is shot and at least one cell in it is not accepting a charge and its acting as a resistor instead.

You need to do a charging load test. Aircraft running and a load tester attached that will draw something close to the rated output in amps of the charging circuit.

Or just get an external known working clamp ammeter attached to the battery cables and confirm there's no amps going into the battery after an engine start below the set point of the voltage regulator.

(Or there's a couple of other ways to do it.)

But the log clearly shows a falling voltage over time from the moment you removed the external battery charger.
 
I agree, your alternator is not charging the battery. You are running on the battery alone. Check the wiring and connections from the alternator to the battery. If connections are good, then check the voltage at the output of the alternator...it should be 13.5+ when running.
 
Quick update: Saturday my mechanic changed the regulator setting on the VR to boost the voltage, started the engine and my GPS was running at 13.6v with a much larger + deflection showing on the ammeter. Buttoned everything up and took off. In flight, with everything on (meaning master switch & avionics master, strobes, etc.) the voltage on the GPS dropped back down to 12.4-ish. So I stopped 1/2 way for fuel and once clear of the runway while taxiing in I flipped off the avionics master. Voltage went back up to 13.6.

So now what I think I need to do is turn off the Com1 radio, transponder, and the audio panel and power each one up individually to try to isolate which one is causing the voltage drop. Ultimately, I'm still in the dark but it seems like it's in the avionics circuit? More testing is in order.
 
It sounds like a bad cell in the battery.
 
iflyvfr said:
Today's observations:

Location Voltage on GPS | RPMs Master Switch | Avionics Status
On ground at TZR: 13.6v, + deflection on Ammeter, 800 RPM, Master Switch ON, Avionics Master OFF;
On ground at TZR: 13.5v, + deflection on Ammeter, 800 RPM, Master Switch ON, Avionics Master ON;
In flight, 1800' MSL, 12.7v, + deflection on Ammeter, 2500 RPM, Master Switch ON, Everything ON;
In flight, 3500' MSL, 12.6v, slight + deflection on Ammeter, 2400 RPM, Master Switch ON, Everything ON;
On ground at TZR: 12.1v, - deflection on Ammeter, 0 RPM, Master Switch ON, Avionics Master OFF;
Click to expand...

A falling system voltage when the RPM is rising is indicative of alternator brush and slip ring problems. If the slip rings are worn out-of-round the brushes start bouncing, the net field resistance goes way up and the output falls because the regulator can't feed any more current to the field. Or the brushes have become so short that they start to chatter, which causes the same thing. I have seen both scenarios. Not common, but they do happen. Alternators need 500-hour internal inspections just like magnetos.
 
Thank you Dan. It has been six years and probably pretty close to 500 hours since the alternator went in. Much to think about and troubleshoot in this thread. Unfortunately my mechanic is not on my field so we have to wait until weekends typically to figure this out. And he has a personal life as do I so things like this can stretch out a bit.
 
Axtel4 said:
It sounds like a bad cell in the battery.
Click to expand...

Wouldn't be enough resistance to pull the alternator voltage that far down in flight now that he's turned it up.

Something is wrong on the charge side of things.
 
This screams corroded or loose connection to me. I'd start with the battery terminals, then the alternator and voltage regulator connection. I'd check for looseness then corrosion.
 
The battery terminals are squeaky clean. The VR connections look good and are tight, same with the alternator side. I'll post more clues after Thursday when I'll perform my testing on the avionics.
 
I thought I'd provide some additional data points. Sunday I went out to do more testing: checked the voltage with the master on and it showed 11.9 on the GPS. That's with master on, but avionics master off. So I thought I'd take it flying since it was a beautiful evening. As I started up, I noticed the ammeter needle bouncing pretty significantly. I didn't recall it doing it like that before. Fast forward to now I'm in the air and climbing and not yet clear of the Class D. To my surprise I see this:

So I turned around and landed. I thought I heard some high-pitched rapid beeping, but my hearing is going along w/ my eyesight; would you see if you can hear it in the above vid & let me know? I don't know what would make that noise so I'm sure it was y imagination.

Anyway, I did not put it back on the Battery Minder when finished. I planned to come back in a few days and see how low the voltage at the battery had sunk. I wanted to check a theory that the Minder was masking a bad cell in the battery because I always keep it on the charger/tender. After 4 days, tonight I went out and read the battery voltage directly at the battery, and it read 12.88v. I turned on the master, the landing lights, beacon and GPS and it showed a normal 1-2 needle deflection on the Ammeter and the meter showed a normal drop too. As soon as I shed the load the battery began to recover.

But here's the kicker. We decided to stress the battery a little so master switch on, GPS on, some lights, then avionics switch on. No response: no comms, transponder, audio panel - all dead. That hadn't happened before! I wonder if Desert Nomad in post #41 is going to win a six pack? I'm going out of town and my runway is closed, so it will be a few weeks until we can get back to it, but this is an interesting development and thought I'd share.
 
Something is wrong, I wouldn't fly it again until it's fixed. Short on ideas, but maybe a diode in the alternator?
 
Yeah, I'm thinking an alternator problem, probably a bad diode in the rectifier or possibly a ground issue, I would send a copy of the video to Plane Power. I bet they can tell you what it is right away.


Edit, it looks like you are getting ac to the bus, can't be good for your avionics.
 
Paul, thanks I'm curious what tells you I'm getting AC to the bus? The bouncing ammeter mimicking the flow of alternating current? FWIW, the GPS is on the master switch although you can see it's swinging fairly widely too. Note: I'm not an electrician or particularly mechanically inclined so I'm genuinely curious as an owner.
 
iflyvfr said:
Paul, thanks I'm curious what tells you I'm getting AC to the bus? The bouncing ammeter mimicking the flow of alternating current? FWIW, the GPS is on the master switch although you can see it's swinging fairly widely too. Note: I'm not an electrician or particularly mechanically inclined so I'm genuinely curious as an owner.
Click to expand...

Yes. A DC meter showing positive and negative fluctuating rapidly is AC.

Easy to confirm if you don't trust the on board ammeter. A multimeter hooked to the bus in AC mode shows any voltage reading at all when the engine is running and the alternator is on, there's AC on the DC bus.

A test you could have done in flight if you have a split master, would have just been to turn the alternator off and leave the battery on. If the ammeter stops bouncing and the voltage displayed on the GPS is a little low but steady, you've found the culprit.

I'd put money on it that at least one of the diodes on the alternator is bad after seeing that. It has failed shorted and not open because you're seeing a negative swing. (Failed open, you'd see pulsed positive DC.)

Which also explains why the battery isn't charging in flight and things die after a few hours. Not good for the battery or anything else.

The tender is the only time the battery is charging correctly, which is something I said earlier. The airplane works okay for a couple hours and on the way home the avionics start to crap out, right?

I suspect the tender is not at fault here. In fact, it's probably why this wasn't fixed sooner. The airplane without a tender would not be charging the battery properly and it would be dead or nearly so, every time you went to start it. The tender is hiding the real problem because it's charging the battery between flights. The mechanic would have looked harder if the airplane was unusable. The tender is making it flyable for a while.

AC is generally bad for everything else in your panel also, but they have their own diodes in their power supply inputs so they're running as long as the voltage averages enough on the positive swing that their own rectifiers can handle the AC.

The meter on the GPS is also showing an average of the voltage getting to it of the correct polarity. It won't see the negative swings because of the diode in its power supply. The meter is past that point inside the radio. It only sees the average of the correct polarity swing.

Of course confirm this or have the mechanic do it. It's literally a five minute job and a good multimeter hooked to the bus and a check for AC present should have been done the FIRST time you had it to him when you said you had charging problems and things dropping off line in flight. Alternator diodes failing is pretty common.

So... confirm and get that alternator fixed. And then you'll probably be able have to turn that voltage regulator back down (more accurately it'll have to be set to the proper voltage for your battery chemistry) afterward too. It wasn't the problem either.

That's my guess. Like I said, this is stuff anyone looking at an aircraft electrical system should have tested the first time they touched it and it's easy to find and confirm. Maybe yours wasn't quite this bad at first and the dead diode is slowly getting worse but by the time it wouldn't charge the battery properly it wouldn't have been hard to diagnose.
 
Hi Greg, Nate explains it very well. Essentially an alternator generates AC power (alternating power) and most have an internal rectifier that converts the AC to DC. Alternating power will change polarity in a sinusoidal pattern from positive to negative. If you had a volt meter on it (without the battery connected to it) you would see the needle swing from a positive voltage to a negative voltage, assuming it could keep up. What you are seeing is the charge rate go from positive to negative as the polarity changes and the broken alternator applies negative voltage to your battery. I would not turn my avionics master on again with the engine running until this is fixed. Plane power has probably seen this many times before and I'm sure could recommend a fix which will probably be repair or replace the alternator. Let us know how you make out.
 
An alternator is an AC generator alright, but at a high frequency. Think 10K Hz in cruise. An ammeter needle has no hope of following that.

A shorted diode just shorts the output from the other diodes and makes the alternator pretty much dead. And a shorted diode should get hot enough to burn open very quickly.

I would suspect that one of the resistors in the voltage regulator is shot.
 
Dan Thomas said:
An alternator is an AC generator alright, but at a high frequency. Think 10K Hz in cruise. An ammeter needle has no hope of following that.

A shorted diode just shorts the output from the other diodes and makes the alternator pretty much dead. And a shorted diode should get hot enough to burn open very quickly.

I would suspect that one of the resistors in the voltage regulator is shot.
Click to expand...

I forgot it was that fast. Been a whole lot distracted lately. You've got a point there. Little weird for the voltage regulator to be able to bounce that thing so far negative thought isn't it?
 
Thanks guys I'm taking it all in for the next time we can TShoot the issue. I've tried to call Plane Power a couple more times but time is limited and I'm now out of town. I appreciate the insight & promise to update my findings
 
Update: a month later and back from Boothbay Harbor IMG_6606.jpg we hope to have the end of the tunnel in sight now. After some more back and forth with tech support, he finally decided we should run a wire from the positive terminal on the battery to the Enable position on the VR in order to isolate the master switch and its components from the loop. VRArrows.jpg This was just for a ground run so my A&P built one from some pieces parts.wire.JPG First we checked the new wire for continuity - we'd had an issue with a flaky jumper wire that goes from sense to enable (shown in the pic above). Then my mechanic disconnected the wire from the Alternator to the Enable position and replaced it with the new end. Satisfied we were secure, I hopped in and started the engine. The problem did not go away.

This was actually good news because the premise was that by isolating the internal master switch from the VR, if the problem DID go away the issue had to be inside the cockpit. Since the problem remained, it meant it could only be two things. fwall.jpg We pulled the VR off the FW and shipped it back for testing. Today support called me back to to say the VR had failed bench testing. You owners can appreciate my relief as I ordered a new R1224B 14v regulator for $200. It should be here Friday. Stay tuned...
 
Hope so, time for some great fall/winter flying ahead, already missed some but the trip to Maine helped scratch the itch a bit, albeit courtesy of SW Airlines.
 
It's great when one locates an issue that has been biting back for so long. I hope you get everything put together and can go flying this weekend.
 
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